Let
me summarize- from the literature that we are engaged in reviewing- the various
things that said to be distinctive of human behavior and are made the basis for
saying that man differs in kind from the animals. With one exception of language
(sentence-making behavior), there are minority dissents on all these
indications of man’s uniqueness in kind- dissents that treat these indications
as signifying only superiority or uniqueness in degree.
In
the sphere of what is plainly overt and observable behavior:
1.
Only man employs a propositional language, only man uses verbal symbols, only
man makes sentence; ie., only man is a discursive animal.
2.
Only man makes tools, builds fires, erects shelters, fabricates clothing; ie., only
man is a technological animal.
3.
Only man enacts laws or sets up his own rules of behavior and thereby
constitutes his social life, organizing his association with his fellows in a
variety of different way; ie., only man is a
political, not just a gregarious animal.
4.
Only man has developed, in the course of generations, a cumulative cultural
tradition, the transmission of which constitutes human history; ie., only
man is a historical animal.
In
the sphere of interpreted behavior, involving an admixture of interfere from observation:
5.
Only man engages in magical and ritualistic practices; ie., only man is a religious
animal.
6.
Only man has a moral conscience, a sense of right and wrong, and of values; ie., only
man is an ethical animal.
7. Only
man decorates or adorn himself or his artifacts, and makes pictures or statues
for the non-utilitarian purpose of enjoyment; ie., only man is an
aesthetic animal.
These
wholly or partly overt forms of behavior, said by the majority of the
scientists in this group to be distinctive of the human species or genus are
often interpreted by them as implying the presence in man of psychological
processes or abilities that are not present in other animals. Distinguishing between what they call
perceptual and conceptual thought, or between generalization of the sensory
level and the formation of abstract concepts, they attribute conceptual
processes or the ability to form abstract concepts to man and to man
alone. They ground this attribution-
this inference to unobserved processes or abilities- on the fact that
propositional speech, toolmaking, and cumulative
cultural transmission all involve a transcendence of, or emancipation from the
immediate environment as that is momentarily present to the senses; and so, in
their view, these distinctively human performances must have their basis in
psychological processes or abilities that go beyond sense perception and even
beyond sensory residues, such as images.
Let
me repeat: among scientists who consider the matter, there is unanimous
agreement that man and man alone uses verbal symbols and has a propositional
language and syntactically structured speech.
The
fact that up to this date the scientific study of animal communication has not
turned up infirmative evidence by discovering
sentence-making animals by no means precludes the possibility that science in
the future, perhaps seven the very near future, may do so. At least we must fact with a completely open
mind work now ongoing with the bottle-nosed dolphin, and also with chimpanzees
and dogs- work that may show either that other mammals have a propositional
language of their own or that they are capable of learning and using ours. On the other hand, having an open mind about
future possibilities should not be equated, as unfortunately it sometimes is,
with having an undecided mind about present actualities; for we are obliged, at
any time, to judge in light of the evidence that is then available. At this moment, there are no scientific data infirmative of the proposition that only man has a
propositional language.
Apart
from the dance language of the bees, no form of animal communication, instictive or learned, appears to involve declarative
statements. In all other case, animal
communication takes the form either of expressive outcries and gestures, or of
making and responding to signals; there is no naming or stating.
Man
has the power of propositional speech because he has the power of conceptual
thought, whereas the non-human animals lack the power of propositional speeech because they lack the power of conceptual thought.
In
order to establish a radical difference in kind, it is not enough to show that
certain psychological processes or factors are present in man that are not
present in non-linguistic animals.
Should they succeed in showing only this, they do no more than remove
one of the two grounds on which the difference in kind can be regarded as
superficial; namely, the explanation of it by reference to a psychological
continuum of degrees. The other ground
remains untouched. Even if the power of
conceptual thought, present in man and absent in non-linguistic animals,
explains man’s unique linguistic performance, the presence of conceptual
thought in man and its absence in non-linguistic animals may itself be fully
explained by the fact that man’s brain is above a critical threshold in
continuum of degrees of neurological magnitude and complexity. If it can be so explained, then the
difference in kind between linguistic and non-linguistic animals remains
superficial, in spite of the fact that we have here not only a behavioral
difference in kind but also a psychological difference in king, ie., a difference between the kind of psychological factors
that must be posited to explain linguistic behavior and the kind of
psychological factors needed to explain non-linguistic behavior.
On
the critical side, these writers [Sellars, Crichtley and White] make three contributions to the
contemporary consideration of the mixed question about man.
First
and foremost is their distinction between what might be called two modes of
meaning or significance. This has, as we
shall see presently, a direct critical impact on the equivocal use of the word
“symbol” by the comparative psychologists- to cover, without distinction, both
the elements of human speech and what they call “non-verbal symbols” in animal
behavior.
James
and White call attention to the fact that only men invent or institute sign or
symbols by convention, whereas the signs that animals respond to or employ are
natural elements in their experience or behavior. White and Crichtley
introduce a distinction between two types of signifiers- between what they call
“signs” in animal behavior and what they call “symbols” in human behavior. This distinction is much more clearly
expressed and more fully developed by Cassier...
Cassier distinquishes between signals that function operatively in
animal behavior and the symbols that function as designators, describers, or
referents in human behavior. Having
pointed out that symbols “which have an objective reference or meaning” are
totally absent from animal behavior, Cassier then
goes on to say:
Symbols- in the proper sense of the term- cannot be reduced to mere signals. Signals and symbols belong to difference universes of discourse: a signal is part of the physical world of being; a symbol is a part of the human world of meaning. Signals are “operators”; symbols are “designators”.
The
second critical point made by these contemporary philosophers, and by such
scientists as Crichtley and White, turns on their
making a sharp distinction between perceptual and conceptual thought. This distinction is implicit in the
observation that animal thinking is confined to the perceptual environment,
whereas human thinking transcends the immediate environment and extends not
only to objects in the remote past and the remote future, but also to objects
that have no temporal locus whatsoever.
Precisely because they are incapable of conceptual thought, animals,
these writers contend, are not only (1) incapable of sentence-making that
includes statements about the past and future, (2) unable to fabricate tools for
remote future use, (3) devoid of a cumulative cultural inheritance that
constitutes a long historical tradition, but they are also (4) incapable of any
behavior that is not rooted in the perceptually apprehended present situation.
I
have use the word “thought”, as Price and many others do, with measure
equivocation to cover both perceptual and conceptual thinking, in order to
express the critical point here being considered. The question is not whether animals can
think, any more than it is, as we shall see later, whether machines can
think. Animals certainly can think, in
the sense of learning from experience, generalizing, discrimination, and
abstracting, solving problems by trial and error or by insight, and even, as
Price, following Hume, points out, making inductive inferences from empirically
learned cues or signals. The evidence is
both plain and ample that they can think in all these ways. But it is equally plain from the observations
of their behavior, in the laboratory or in the field, that they cannot think in
any of the following ways: they cannot think about objects that are not
perceptually present as well as about those that are; and with regard to
objects of thought, present or absent, they cannot make judgments or engage in
reasoning (ie., think that such and such is or is not
the case, or think that if such and such is the case, then so and so is not).
Among
the authors whom we are here considering, William James is,
of course, a most astute observer and analyst of the difference between
perceptual and conceptual though. Two of
the more recent writers- Geach and Bennett- not only
sharpen the distinction, but also ably defend it with reference to experiments
on generalization and perceptual abstraction in animals, and on problem-solving
by trial and error and by insight.
Geach argues that the experiments that demostrate
an animal’s capacity to recognize triangles or to discriminate between
triangles and quadrangles (functioning as perceptible cues or stimuli) do not
indicate that the laboratory animals have formed concepts of triangularity or quadrangularity. In his view, the laboratory date can be
adequately explained without positing concept formation in animals. To do so is to confuse perceptual abstraction
on the part of animals with human concept-formation which Geach
convincingly shows, does
not consist in a process of abstraction at all.
Bennett
argues that animal learning and problem-solving, whether by trial or error or
by insight, does not involve any of the steps that constitute reasoning from
experience- the process whereby human beings either establish an empirical
conclusion or refute one. Since that
always involves the separate acknowledgment of a timeless universal, on the one
hand, and of particular instances of past occurrence, on the other, animals,
whose apprehensions are limited to the immediate perceptual present, cannot
possibly engage in the kind of thinking that consisting of giving reason pro
and con. And, Bennett further contends,
behavior that involves giving or receiving reasons cannot be causally explained
by reference to empiral sequences. In his view, there can be no behavioristic account of human rational behavior, as there
can be of animal learning and problem-solving, in terms of causal connections between
stimuli and responses or by reference to the causes at work in the formation of
the conditioned responses or imprintings that
represent the modifications of animal behavior through repeated experience.
The
analyses offered by Geach and Bennett, together with
the adverse appraisal that they make of the significance of the experimental
data on animal behavior with which they are aquainted,
amount to a refutation of the interpretation placed upon these data by a large
number of comparative psychologists, especially those of a behaviorist
persuasion. Geach
and Bennett are, in effect, saying that the date can be adequately explained
without attributing either concept-formation or rational judgment to
animals. Hence, to posit the presence in
animals of non-verbal concepts, non-verbal judgments, and non-verbal reasoning
is to violate the very principle of parsimony on which the behavioristic
psychologists are themselves so insistent.
Not to attribute the power of concept-formation and of rational judgment
to man is an equal and opposite violation of the other side of Occam’s two-edged razor, since human behavior- naming
things and uttering sentences that can be true or false- cannot be adequately
explained without positing the power of conceptual or rational thought on the
part of men.
4. REFUTATION OF THE PIVOTAL ISSUE: (1) THE NEGATIVE ARGUMENT
Which
psychological explanation is correct?
That is the nub of the question in this pivotal issue. The ultimate criterion of theoretical
correctness, to which both side do or certainly should appeal, is the principle
of parsimony. The principle works two
ways: on the one hand, it works negatively by imposing the stricture that no
theoretical constructs should be resorted to that can be dispensed with in
explaining the phenomena: on the other hand, it works positively by relaxing
that stricture in the direction of justifying the employment of whatever
theoretical constructs may be needed to explain the phenomena.
It
is this double aspect of the principle of parsimony that I had in mind earlier
when I said that Occam’s razor is a two-edged
instrument- one that works in opposite directs.
It eliminates theoretical constructs that cannot be shown to be
necessary for explanatory purposes; but it also justifies the retention of
theoretical constructs the need for which can be shown.
I
propose that the non-verbal thought processes of animals- processes that remove
the animal, in one way or another, from the domination of the immediate sensory
stimulus- consist in (a) perceptual traces or residues, and (b) perceptual
attainments. By perceptual traces or
residue, I mean memory-images that function representatively, ie., in
place of sensory stimuli that are no longer themselves operative. By perceptual attainments I mean the products
of perceptual generalization and discrimination. I will use the term “perceptual abstraction”
to name such products. Since all these
elements are perceptual- either the consequences, or
the products of perceptual activity- its we3ems fitting to identify the thought
processes in animals with perceptual thought.
This is in line with the proposed hypothesis that the power of
perceptual thoughts, its processes and products, are the only theoretical constructs
needed to explain animal behavior.
A
word more must be said about the perceptual abstraction, resulting from
perceptual generalizations and discriminations that are learned. By a perceptual abstraction in an animal I
mean a disposition to perceive a number of sensible particular (or, in
laboratory parlance, stimuli) as the same in kind or as sufficiently similar to
be reacted to as the same. For example,
when an animal has acquired the disposition to discriminate between triangles
and circles- in spite of differences in their size, shape, color, or position,
and whether or not they are constituted by continuos lines or dots- that
acquired disposition in the animal is the perceptual attainment I have called a
perceptual abstraction. This disposition
is only operative in the presence of appropriate sensory stimulus, and never in
its absence, ie., the animal does not exercise its acquired disposition to
recognize certain shapes as triangles or certain colors as red when a triangular shape or red patch is not
perceptually present and actually perceived.
A
further point must be made, and it is of the greatest importance. All perceptual abstractions- in animals and
in men- are dispositions that are operative only in the presence of perceived
particulars. But human concepts, even
when they relate to perceived particulars, are not operative only in the
perceptible presence of those particulars.
In addition to concepts of such perceptible objects as dogs and roses,
men attain, through the process of theorizing, concepts of such imperceptible
objects of elementary physical particles and chemical valences. In philosophy they develop concepts of such
imperceptible objects as truth and justice; and in psychological theorizing
they employ concepts of such imperceptible objects as memory-images, perceptual
abstractions, and concepts themselves.
Concepts
of the latter type are the type that we have called theoretical
constructs. They are formed (ie.,
constructed) relating other concepts- conjunctively, disjunctively, by
negation, etc. Only
concepts of the first type (ie. Concepts of
perceptible objects) are formed on the basis of perceptual abstract Yet even these are not formed solely on that basis, but
require, in addition, a process of construction in which concepts are relations
by conjunction, disjunction, negation, etc.
In other words, no concepts are derived solely from perceptual
abstracts; none is simple an abstraction from perceptual experience; all are
constructed, though some are constructed on the basis of perceptual
abstractions and some are not ; and it only the latter
that we call theoretical constructs.
To
summarize: two points made above set up a sharp and clear distinction between
perceptual abstractions and concepts.
(1) As attained dispositions, perceptual abstractions are exercised on
in the actual presence of perceived objects, whereas concepts are exercised
even when the appropriate objects are not actually perceived, and even when
they cannot be, because the objects are imperceptible. (2) Perceptual abstraction are
attained solely by processes that involve the exercise of perceptual power (ie. Perceptual generalization and discrimination), whereas
concepts even those that are concepts of perceptual objects, are never solely
attained by the exercise of perceptual powers.
The
fact that perceptual abstractions and concepts are functionally alike in one respects does not justify the comparative psychologists in
saying that perceptual abstractions are rudimentary concepts. Though the concept of a
perceptible objects is a disposition to discriminate between similar and
dissimilar particulars, it is never solely that, and it is that only in virtue
of being a disposition to recognize each perceived particular as being of a
certain kind and to understand what kind of thing it is. Furthermore, this disposition is operative
when the perceptible objects are not actually being perceived as well as when
they are. Hence a perceptible
abstraction, which is a disposition only to perceive a number of sensible
particulars as similar and to discriminate between them and other sensible
particulars that are dissimilar, and is a disposition that functions only when
the sensible particulars are being perceived, cannot be regarded even as a
rudimentary concept of perceptible objects.
With
my hypothesis sufficiently explication and its constitutive distinctions made
clear enough for the purpose at hand, we are now prepared to look at the
relevant laboratory data, to see whether the experimental evidence supports the
hypothesis proposed, or supports the contrary hypothesis advanced by most
comparative psychologists,
The evidence falls into two sets of finds, the first relevant to
perceptual residues, the second relevant to perceptual attainments.
(1)
The first set of findings consists of evidence derived from delayed-reaction
and detour experiments. The data can be
summarized as follows: (a) In delayed-reaction experiments, the animal,
prevented from reacting immediately to a present stimulus, subsequently reacts,
in the absence of that stimulus, in the way that it would have reacted to the
stimulus at the time it was present, had it not been prevented from doing so The interval of
the delayed reaction varies from extremely short intervals measured in seconds
to a day or tow at the most in a few exceptional cases. (b) In detour experiments, the animal,
blocked from a direct path of reaction to a present stimulus, takes a
circuitous path that removes the stimulus for a time the perceptual field.
(2)
The second set of findings consists of evidence derived from experiments on
equivalent and non-equivalent stimuli, on generalization and transfer, on
animal maze-learning, on cue learning, on discrimination, and on solving
multiple-choice problems. The data can be
summerized as follows. The animal which, by learning or otherwise,
reacts to a particular stimulus or cue in a particular way, transfers that same
reaction to other stimuli or cues that are like it in type, though not like it
in all particular respects.
5. RESOLUTION OF THE PIVOTAL ISSUE: (II) THE POSITIVE ARGUMENT
It
was shown in the preceding chapter that the comparative psychologists
equivocate in their use of the word “concept” when they use this word for a
theoretical construct needed to explain the observed behavior of animals as
well as men. When the difference between
concepts and perceptual abstractions is clearly understood, it can be seen that
all the experimental evidence advanced by the comparative psychologists can be
explained without reference to concept-formation on the part of non-linguistic
animals. The only theoretical constructs
required for the explanation of non-linguistic behavior are perceptual residues
(memories) and perceptual abstractions.
The non-verbal mediating factors operative in the behavior of
non-linguistic animals are memories and perceptual abstractions, not
concepts. Hence if there is a
theoretical justification for dividing concepts into verbal and non-verbal,
that must be derived from human behavior exclusively.
The
same criticism applies to the use of the word “symbol” by the comparative
psychologists. They use the world
without distinction between two quite distinct types of signs- for signals, on
the one hand, and for designators, on the other (ie.,
on the one hand, for the type of sign that smoke is when it signifies fire,
and, on the other hand, for the type of sign that the word “smoke” is when it
signifies smoke). Once the distinction
between these two types of signs or signifiers is clearly understood, it will
be seen that the behavior of non-linguistic animals can be fully explained in
terms of signals without reference to designators. It can, furthermore, be shown that animals
respond to verbal as well as non-verbal designators. Hence, it is not the distinction between
verbal and non-verbal that differentiates human from animal behavior in the use
of symbols, but rather the distinction between designators (verbal and
non-verbal) and signals (verbal or non-verbal).
Because
the word “symbol” has been used by so many writers in so many different sense, I propose to discard it entirely, and to replace it
by the world “signifier” or, in shortened form, by the word “sign”. The latter is visibly present as the root of the
words “signal”: and “designator”, which I will use for the two main types of
signifiers. In these terms, it will be
the task of this chapter to show that (1) the behavior of non-linguistic
animals involves the use of signals, but never designators, (2) that human
behavior involves both, (3) that the functioning of signals in the behavior of
non-linguistic animals does not require concept formation on their part, (4)
that the functioning of designators in human behavior cannot be explained
without attributing the possession of concepts to man.
Of
these four points, the last two are critical for the resolution of the pivotal
issue concerning the difference between man and other animals. The establishment of the third point (that
the functioning of signals in the behavior on non-linguistic animals does not
require concept-formation on their part) will confirm the negative argument set
forth in the preceding chapter. The
establishment of the fourth point (that the functioning of designators in human
behavior cannot be explained without attributing the possession of concepts to
man) will constitute the positive argument that is needed to complete the
resolution of the issue; for it is not enough to show negatively, that the
behavior of non-linguistic animals can be psychologically explained without
employing concept-formation as a theoretical construct. It is also necessary to show, positively,
that the psychological explanation of man’s linguistic behavior must employ
concept formation as a theoretical construct.
When
these two things have been shown, we shall be warranted in concluding that
there is a psychological difference in kind between man and other animals- a
difference in kind that turns on the use of concepts by man and not by other
animals. That conclusion still leaves
open the question whether the difference in kind is superficial or radical, as
the opposite conclusion would not; for it the same psychological factors or
processes, accompanied by differences in degree, could explain linguistic and
non-linguistic behavior, we would know that the difference in kind between man
and other animals, manifested by man’s exclusive possession of a propositional
language, was only a superficial, not a radical difference in kind.
Since non-linguistic animals do not use verbal designators, since they do not react to verbal designators as designators, by only as cues, and since the functioning of cues, verbal or non-verbal, can be adequately described in terms of the instinctive or learned responses that they elicit, without reference to meaning, their functioning can be satisfactorily explained without attributing concept-formation and concepts to non-linguistic animals.
6. THE EFFORTS OF THE PHILOSOPHERS TO RESOLVE THE ONE ISSUE THAT REMAINS
What
has been established so far in the light of all the evidence that is present available? Two things. (1) On the level of observable behavior, no
affirmative evidence as yet exists to falsify the proposition that man and man
alone possesses a propositional language.
The truth of this proposition carries with it the truth of the
proposition that there is a manifest difference in kind between man and
non-linguistic animals. (2) On the level of the psychological explanation of
the observed behavior of both linguistic and non-linguistic animals, the
application of the principle of parsimony produces two results. (a) The
negative edge of Occam’s razor cuts away the grounds
for attributing to non-linguistic animals anything beyond the power of
perceptual thought, in order to explain their behavior. (b) Its positive edge supplies the
justification for attributing the power of conceptual thought to man and to man
alone, since man’s ability to name or designate objects and to makes
significant declarative sentences about them cannot be explained except in
terms of man’s having the ability to understand what different kinds of objects
are like and his having the ability to make judgments about them in the light
of such understanding. These two
abilities together with the additional ability to draw inferences from the
judgments made or to construct arguments out of them,
constitute the power of conceptual thought, the root of which is the ability to
form and employ concepts.
The
two aforementioned results of applying the principle of parsimony to
psychological explanations of linguistic and non-linguistic behavior establish
the truth of another proposition concerning the difference of man; namely, that
man differs in kind from other animals on the level of inferred psychological
factors or processes as well as on the level of observed behavior. The establishment of this proposition
resolves the pivotal issue in the controversy about man. Since this leaves quite open the question
whether the manifest and psychological difference in kind between man and other
animals is superficial or radical, one issue still
remains.
The
questions at issue can be stated in a number of ways. One way of stating it is to ask whether, on
the level of the neurological explanation of man’s observed behavior and the power
of conceptual thought that must be posited in order to give a satisfactory
psychological explanation of linguistic behavior, no factors or processes need
be posited that are not employed in giving a neurological explanation of the
behavior of non-linguistic animals. If
this question can be answered by showing that the only neurological difference
between man and other animals, needed to explain man’s having and other
animal’s lacking a propositional language and the power of conceptual thought,
consists in a difference in the degree of brain magnitude and complexity, then
the issue can be resolved in favor of the proposition that man’s difference in
kind is only superficial, not radical.
The statement just made must be expanded by adding one critical point:
it must be shown that, in the continuum of degrees of brain magnitude and
complexity, there is a threshold above which propositional language and
conceptual thought occur and below which they do not; and that the size and
complexity of man’s brain lies above this threshold, and the brains of all
other animals fall below it.
Another
way of stating the question at issue is to ask whether the power and action of
the human brain is not only a necessary, but also the sufficient, condition of
man’s having and exercising the power of conceptual thought, without which he
could not exercise the power of propositional speech. The power and action of the human brain
constitute the sufficient condition of conceptual thought if conceptual thought
can be adequately explained in terms of neurological mechanisms and
processes. They constitute only a
necessary, but not the sufficient, condition of condition of conceptual
thought, if conceptual thought cannot be explained without reference to
neurological mechanisms and processes, but if it also cannot be adequately
explained by reference to them. If, on
the first alternative, we were to find that the brain is the sufficient
condition of conceptual thought, then we would be justified in concluding that
there is probably a critical threshold in the continuum of degrees of brain
magnitude and complexity, below which conceptual thought does not occur, and
above which it does. If, on the second
alternative, we were to find that the brain is only a necessary, but not the
sufficient, condition of conceptual thought, then, even though there might
still be a critical threshold in the continuum of brain magnitude and
complexity, this could not by itself explain man’s possession of the power of
conceptual thought that is totally lacked by non-linguistic animals. Hence, in the first alternative, man’s
difference in kind would turn out to be superficial; in the second, it would be
radical.
Still
another way of stating the question is to ask whether the human brain, together
with the entire sensory and motor apparatus that are its integral appendages,
is the organ of conceptual thought in the same sense that it is the organ of
perceptual thought (ie., of sensations and sensory
affects, of perceptions, perceptual residues such as sensitive memories and imemory-images, and perceptual attainments such as
perceptual abstractions), and of the initiation of all the bodily movements or
reactions consequent thereon. One answer
to this question claims that the brain is the organ of conceptual thought and
of the linguistic behavior consequent thereon in exactly the same sent that it
the organ of perceptual thought and of the non-linguistic behavior that is
thereby initiated. The opposite answer
claims that, while the brain is an organ indispensable to conceptual thought
and linguistic behavior, it is not the organ of conceptual thought in exactly
the same sense that it is the organ of perceptual thought. The first answer leads to the conclusion that
man’s difference in kind from linguistic animals is only superficial; the
second, to the conclusion that the difference is radical.
For
the purpose of the present inquiry, the only question that concerns us is
whether conceptual thought can be adequately explained in neurological
terms. The hypothesis that it can is
currently called the “identity hypothesis”, and when I call the position that
adopts that hypothesis the “materialist position”, I mean materialism in a
sense that is acceptable to the exponents of the identity hypothesis and the monistic
or reductive materialism that they so explicitly reject. The opposite hypothesis, that I have called
the “immaterialist position”, might also be called the “non-identity
hypothesis”, since it affirms mind as an immaterial power that is existentially
and causally distinct from the brain and nervous system.
The
argument for the identity hypothesis, boiled down to its essentials, involves
three steps. (1) All the empirical evidence now available shows that the brain
is a necessary condition of sensory or perceptual occurrences and processes, ie., the
latter have never been found to occur without the accompaniment of brain events
or processes. (2) in view of the fact that the psychic
phenomena in question can be experimentally produced by activating the central
nervous system in certain specified ways, brain act is only a necessary
condition in the sine of sine qua non, but also the productive cause of the
psychic phenomena in question. (3) Since there is no need for an additional
cause, or a cause of another type to explain the phenomena, the principle of
parsimony operates to make the action of the brain not merely a necessary, but
the sufficient condition of sensory or perceptual occurrences or processes-
everything that can be ascribed to the exercise of the power of perceptual
thought.
The
opponents of the identity hypothesis as applied to conceptual think do not deny
that neurological processes may be an indispensable or sine qua non condition
of conceptual thought, but they argue that the meanings- or, in their language,
the “intentionalities”- which are identical with
concepts and which confer significance on the name or designators that we use
in propositional speech cannot be adequately explained in neurological terms;
and so the action of the brain and nervous system is not the sufficient
condition of conceptual thought.
Professor Popper’s way of saying this is summarized in his thesis that
“no cause physical theory of the descriptive and argumentative functions of
language is possible”; in other words, no neurological or mechanical
explanation can be given of the meanings involved in our use of designative
names, and even less so of the meanings involved in sentences whereby we
express inferences. Professor Price of
Oxford, in a discussion of papers on the mind-body problem by Anthony Quinton,
also of Oxford, and John Beloff of Edinburgh,, points
out that “if Brentao is right in saying that all
mental events have intentionality and that no physical events have its, this
would seem to be a conclusive objection to the Identity Hypothesis.”
To
summarize the discussion we have just surveyed, I would call the reader’s
attention to three points.
(1)
The positive argument for the identity hypothesis, as advanced by Sellars and Craik, has its crux
in the parallelism or analogy between the order and relation of concepts in
thought and the order and relation of the verbal elements of propositional
speech. Turning on that crux, the
argument proceeds as follows: a similar parallelism can be found between the
order and relation of verbal elements and the order and relation of neural
events or of computer states; it should, therefore, be possible to explain
language in neurological or mechanical terms; and if that is possible, it
should be possible to explain conceptual thought in neurological or mechanical
terms. Sellars
and Craik do not assert that a completely
satisfactory or adequate explanation has yet been given; they merely contend
that they see no difficulty in principle in giving one.
(2)
The opponents of the identity hypothesis, especially Popper and Price, base
their criticism of it on the intentionality or meaning that constitutes the
elements of conceptual thought; concepts
that the intentions or meanings through which all signs; both verbal and
non-verbal, get their significance. They
then argue as follows: since that which is mental is intentional and that which
is physical is not, they cannot be identified; nor can an adequate physical
explanation be given of the intentionality that is constitutive of elements of
conceptual thought.
(3)
Against such criticism, the defenders of the identity hypothesis point out that
their theory does not call for the analytical inseparability or indistinquishability of the mental and the physical- the
intentional and the non-intentional. It
asserts only that they are existentially inseparable in an empirical and
contingent manner. This being so, the
action of the brain is at a least a necessary condition of conceptual thought;
and there is good reason to suppose that it is also the sufficient condition,
in view of the purely mechanistic explanation of man’s propositional speech
that can now by structural linguistics and empirical semantics.
In
the hylomorphic doctrine that is Aristotle’s most
original contribution, it is impossible for the mind-body problem to arise,
either on the preceptual on on
the conceptual level. And after it has
arisen in Cartesian or post-Cartesian terms, it is impossible to translate it
back into Aristotelian terms in order to pose the problem in a way that an
Aristotelian could understand well enough to try to solve it. The point is not that there is no
Aristotelian solution to the mind-body problem; the point is rather that,
within the framework of Aristotelian metaphysics and psychology, there can be
no mind-body problem.
In
the hylomorphic view of being and becoming, of
inanimate and animate nature, of man, the twin pair of polar principles- matter
and form, potency and act- lead to the conception of the soul as nothing but
the form and the first actuality of an organic body having the potentiality of
life; and all vital operations, from digestion and locomotion to imagination
and conceptual thought, are the second acts (or actualizations) of the living
organism’s power or potentialities. In
this view, the soul is inseparable from the organic body of which it is the
form, just as the seal impressed on the wax is inseparable from the wax; and
this applies to the human or rational soul just as it applies to the sensitive
souls of plants. What is true of soul as
the form or act of the organic body as a whole is also true, with one
exception, of the parts of the soul, ie., each of its various powers is the power of a part of the
body, a living organ. Thus, the power of
digestion is embodied in the stomach; the power of vision, in the eye and the
brain; the power of memory or imagination, in the brain; and so on.
The
one striking exception, according to Aristotle, is the power of understanding
or intellection- the power of conceptual thought. This one power (distinctive of the rational
soul that is the form of the human body) belongs to the living or besouled man in exactly the same way that his power of
digestion or his power of perception does; but unlike all his other powers, this
one power is not the power of any bodily organ.
It alone is an immaterial power; its acts are not the acts of any bodily
organ; yet its acts never occur without the accompaniment of sensory or
perceptual acts, especially acts of imagination and memory, that are themselves
acts of corporeal power, ie. Acts
of the sense organs and of the brain.
The
immateriality of the intellectual or conceptual power does not create a
mind-body problem for Aristotle; for, as I just remarked, this immaterial
power, no less than the other corporeal powers, belong to man the living
organism, composite of matter and form; it functions co-operatively with other
corporeal powers (ie., affects them and is affected
by them), especially man’s sensory or perceptual powers; and it cannot function
in any other way because man is a unity both in existence and in operation.
I
hope this brief digression into Aristotelian theory has now explained why I
regard it as paradoxical that Aristotle and his follower Aquinas should supply
us with the one argument for the immateriality of the power of conceptual
thought that fits into the contemporary dispute of the mind-body problem as a
mixed question, involving both science and philosophy, so far as that problem
involves the question of whether conceptual thought can be adequately explained
in neurological term (ie., whether the action of the
brain is the sufficient cause of conceptual thought), and so directly bears on
the question whether man’s difference in kind from non-linguistic animals is radical
or only superficial.
The
argument in its bare bones hinges on two propositions. The first proposition asserts that the
concepts whereby we understand what different kinds or class of things are like
consist in meanings or intentions that are universal. The second proposition asserts that nothing
that exists physically is actually universal; any that is embodied in matter
exists as an individual; and as such it can be a particular instance of this
class or that. From these two
propositions, the conclusion follows that our concepts must be immaterial. If they ere acts of a bodily organ such as
the brain, they would exist in matter, and so would be individual. But they are universal. Hence, they do not and cannot exist in
matter, and the power of conceptual thought by which we form and use concepts
must be an immaterial power, ie., one the acts of which are not the acts of a bodily organ.
The
reasoning that supports the first proposition is as follows. Our common or general names derive the
meanings they carry from the concepts we have.
The meaning of a common or general name is universal in its denotation
and its connotation; that is to say, a common or general name always signifies
a class of objects, never any particular instance or member of the class. Therefore, the concept that confers meaning
on a common or general name must be a universal meaning- an act of the mind
which has an intentionality that is universal.
Were it otherwise, the concepts that we form when we exercise our power
of conceptual thought would not enable us, as they do, to understand what it is
like to be a dog, or a poodle, or a quadruped- or an electron, a galaxy or so
on.
The
second proposition is supported by the facts of common experience. The objects of our common experience are all
individual things, ie., this individual dog, or poodle, or quadruped. One and the same individual object may be a
whole variety of particulars according as it is a member of whole variety of clases; the object lying at my feet is this one unique
individual thing, but is many particulars, for it is this particular dog, this
particular poodle, this particular quadruped.
The same holds true of objects outside the domain of common experience,
such as theoretical entities that are posited objects of scientific
knowledge. Each elementary particle
moving about in a cyclotron is that one individual particle, thought this
individual particle may be a particular electron, and that particular particle
may be a particular neutron.
The
facts just state lead to the generalization that all physical objects, whether
they are objects of common experience or objects of scientific knowledge, are
individual things. This generalization
can be stated in the following proposition and its converse: the proposition is
that whatever exists physically (ie., whatever is embodied in matter) exists as an individual;
and the converse proposition is that whatever exists as an individual exists
physically. Since these two propositions
state empirical generalizations, they are capable of being falsified by a
single negative instance. But no
negative instance has yet been found; no one has ever produced an existent
object of common experience or of scientific knowledge that is at once physical
or material in its most of existence and also universal in character (ie., a
class of things rather than an individual thing.)
The
argument then reaches its conclusion as follows. Our concepts are universal in the character
of their intentionality. Hence they do
not exist physically; they are not embodied in matter. Since our concepts are acts of power of
conceptual thought, that power must itself be an immaterial power, one not
embodied in a physical organ such as the brain.
The action of the brain, therefore, cannot be the sufficient condition
of conceptual thought, thought it may still be a necessary condition thereof,
insofar as the exercise of our power of conceptual thought,
depends on the exercise of our power of perception, memory and imagination,
which is a corporeal power embodied in our sense organs and brain. (If it can be shown that any other animal,
such as the dolphin, has the power of propositional speech and therefore, the power
of conceptual thought, the argument just stated would lead to the same
conclusion about the dolphin; namely, that it had an immaterial power and that
the action of the dolphin brain may be a necessary, but cannot be the
sufficient, condition of the dolphin’s engaging in propositional speech and
conceptual thought.)
But
the non-identity hypothesis that I have described as a moderate immaterialism-
the theory of intellect or mind developed by Aristotle and Aquinas- appears to
be totally neglected in the contemporary discussion. From Ryle on, the
only theory of mind that the exponents of the identity hypothesis hold up for
ridicule or refutation is the Platonic or Cartesian form of extreme
immaterialism that they interpret as positing the ghost in the machine, and
against which they argue, in terms of the principle of parsimony, that the
ghost need not be posited in order to explain human behavior, including
linguistic behavior and conceptual thought.
This adverse argument does not, of course, apply to the Aristotelian or
Thomistic form of moderate immaterialism.
In facts, the proponents of that position claim that the principle of
parsimony works in the opposite direction to justify positing the immateriality
of the power of conceptual thought in order to explain the universal
intentionality of its acts.
Because
the moderate immaterialism of Aristotle and Aquinas is totally neglected or
ignored in contemporary discussion, we cannot look for criticisms of it, or
objections to it, in current philosophical literature. Aquinas, however, did himself raise one
objection against his own theory; and at least two others can be readily
thought of. I will now present these
three objections, together with replies that are consistent with the position
to be defended.
First objection and reply. The clinical
date of brain pathology, especially brain injuries that are accompanied by
disorders of speech and the loss of understanding, show the involvement of the
brain in the processes of conceptual thought; just as other brain injuries
causing blindness or deafness show the involvement of the brain in perceptual
processes. Hence, the one set of
processes, like the other, must be a function of the brain. This objection is raised by Aquinas, who
mentions the interference with conceptual thought that results from the effect
of toxic substances and fatigue poisons on the action of the brain.
His
reply consists of pointing out that there is no inconsistency between admitting
the involvement of the brain in conceptual thought and asserting the
immateriality of conceptual thought. All
that the evidences of brain pathology show is that the brain is a necessary
condition of conceptual thought; and in order to deny that the brain is the
sufficient condition of conceptual thought, one does not have to deny that it is
a necessary condition.
The
error of the objection consists in treating conceptual and perceptual processes
as wholly alike in beings functions of the brain; ie.,
in treating visual blindness (loss of sight) as if it were the same thing as
conceptual blindenss or agnosia
(loss of understanding). To treat them
the same is to ignore the argument for the immateriality of conceptual
thought. The objection can hardly
invalidate an argument that it ignores.
Second objection and reply. The human
infant is not born able to exercise the power of propositional speech. It is only in the course of maturation that
that power comes into operation and develops with exercise. The infant’s first use of names or
designators and his first utterance of sentences do not occur until, with
growth, the brain reaches a certain magnitude.
Hence, it would appear that there is a critical threshold in the
continuum of brain magnitudes, above which the human being has and below which
he lack propositional speech. But the
presence of propositional speech is our only objective evidence of the presence
of conceptual thought; and so it can be argued that engaging in conceptual
thought depends, as engaging in propositional speech depends, on a certain
brain magnitude.
The
reply to this objection, like the reply to the preceding one, concedes that
conceptual thought depends on the brain, and especially on its having a certain
magnitude. However, all that this shows
is that the brain, or a certain magnitude of it, is a necessary condition of
conceptual thought. The
argument for the immateriality of conceptual thought, the whole point of which
is to show that the brain is not the sufficient condition of conceptual
thought, remains untouched by this objection.
Third objection and reply. It has been
conceded that animals and machines are capable of perceptual abstractions. Rats can learn to react to individually
different triangles as if they has some characteristic in common (their triangularity) that is not shared by other visible shapes;
and some success has been achieved in getting machines to recognize different
shapes in an apparently discriminating manner (ie.,
react in one way to square shapes, and in another to triangular shapes.) It would thus appear that animals and
machines are able to apprehend universals- classes or kinds of objects. But unless an immaterial power is to be
attributed to sub-human animals and to machines, it would seem to follow that
an immaterial power need not be posited to explain man’s apprehension of classes
or kinds of objects. Hence, even if it
is granted that concepts whereby we know kings or classes are universal intentions, that does not justify our positing the
immateriality of the power of conceptual thought.
The
reply to this objection turns on preserving the distinction that was
made...between perceptual abstraction and concept-formation. Let me repeat it briefly here.
A
perceptual abstraction, as attained by men or other animals, is an acquired
disposition to preceive a number of sensible particulars
as being of the same kind or as sufficiently similar to be reacted to in the
same way; it is also a disposition to discriminate between similar and
dissimilar particulars. It is not a disposition to recognize a single perceived
particular as being of a certain kind, for the recognition of a single
perceived particular as being of a certain kind is inseparable from the
understanding of the kind itself. These
related acts of recognition and understanding presuppose more than perceptual
abstraction; they presuppose concept-formation.
In a laboratory rate that has learned a food cue, a perceptual
abstraction or generalization enables it to perceive that this shape or this
shape (eg.,
triangular shapes) but not that shape or that (eg.,
circular shapes) are sufficiently alike to serve as the cue for a certain
response. But such perceptual
generalization and discrimination does not dispose the rate to recognize that
this shape by itself is a triangle or to understand triangularity
when no triangular shapes are perceptually present. Only a man, having the concept of triangularity, can recognize this perceived shape as being
an instance of triangularity, and can, in the absence
of any perceived shape, understand triangularity and
the distinction between it and circularity. By means of a perceptual
abstraction, like that attained by the laboratory rat, a man can also perceive
a number of sensible particulars as similar shapes and discriminate between
them and dissimilar shapes, but his recognition that the similar shapes are all
triangles and that the dissimilar shapes are circles derives from his concepts
of triangle and circle, which operate in conjunction with his perceptual
abstractions.
The
central point here is that perceptual abstractions do not function in the same
way in man, on the one hand, and in non-linguistic animals and in machines, on
the other; because in man they operate in conjunction with concepts and in
other animals and machines, they do not.
Since,
unlike concepts, perceptual abstractions do not have an intentionality that is
universal in character, immateriality need not be
attributed to the power of which they are acts. This holds true for all other acts of the
power of perceptual thought, such as the acts of memory and imagination. Hence, even if these acts have
intentionality, as all cognitive acts do, the type of intentionality they have
is such that they can be acts of bodily organ.
It is only an intentionality that is universal in character and that is
characteristic of conceptual acts, but not of perceptual acts, which warrants
attributing immateriality to the cognitive power. Hence, the object might have some force
against the position held by Brentano and those who adopt his thesis that all
cognitive acts have intentionality in the same sense; but it has no force
against the position of Aristotle and Aquinas, who distinquish
between the intentionality of conceptual and the intentionality of perceptual
acts, and regard them as only analogous because the one is universal in
character and the other is not.
From
the point of view of the moderate immaterialists who oppose the identity
hypothesis solely on the ground that conceptual thought cannot be identified
with the action of the brain, the defence of the
identity hypothesis simply misses the mark.
One way or another, it bypasses the crucial question about the place of
meanings or intentions in the scheme of things- the type of universal meanings
or intentions that constitute conceptual thought and that are the source of
meaningfulness in everything else, especially the meanings acquired by the
originally meaningless vocable or notations that
comprise the common or general names in human language. If that which is meaningless cannot become
meaningful except through that which is, in its very nature and existence, a
meaning, the question about how and where meanings exist would seem to be an
inescapable one.
Proponents
of the Aristotelian and Thomistic theory of conceptual thought would certainly
insist that the question of meanings or intentions, far from being irrelevant,
is the very crux of the issue.
Even
though Aristotle and Aquinas, and anyone else who shares their view, offer a
direct argument for a conclusion that they regard as demonstrable, not
self-evident, they would have no hesistation in
employing the indirect argument concocted by Descartes for the purpose of
persuading those who might not be persuaded by the direct argument, which
certainly describes the condition of adherents of the identity hypothesis.
The
nub of the indirect argument can, therefore, be expressed in the following
challenge: “Show me an animal or a machine that can engage in conversation,
either with another machine or with another animal or with a human being, and I
will either have to concede that matter organized in a certain way can think
conceptually, or I have to posit the operation of an immaterial power in the
machine or in the sub-human animal”.
Translated
into terms that fits the present state of science and technology, the Cartesian
challenge can be somewhat expanded so that it has three distinct prongs. The first prong is a challenge to the
neurologist to give an adequate explanation of conceptual thought in terms of
brain action. The second prong is a
challenge to the zoologist to discover a non-human species of animal the
members of which engage in conversation with one another, or that can be taught
to engage in conversation with members of the human species after we have found
some means of translation between the propositional language of that species
and our own. (This prong of the challenge, it must be noted, is not met by
training circus or laboratory animals to respond to human words; or to imitate
the sounds or even the verbal sequences of human speech, for parrots and myna
birds can do that.) The third prong is a
challenge to the technologist to produce a machine specifically not a computer
but an artifact that, without being programmed to do so, can engage in
conversation with human beings, using as a means not “computer talk”, but an
ordinary language such as English.