There is not much we can do about such metaphors except to state that that is precisely what they are.
Now originally, this search into the nature of consciousness was known as the mind-body problem, heavy with its ponderous philosophical solutions. But since the theory of evolution, it has bared itself into a more scientific question. It has become the problem of the origin of mind, or, more specifically, the origin of consciousness in evolution. Where can this subjective experience which we introspect upon, this constant companion of hosts of associations, hopes, fears, affections, knowledges, colors, smells, toothaches, thrills, tickles, pleasures, distresses, and desires —
where and how in evolution could all this wonderful tapestry of inner experience have evolved? How can we derive this inward-ness out of mere matter? And if so, when?
3 For a statement of this effect, see G. H. Lewes, The Physical Basis of Mind (London: Trübner, 1877), p. 365.
4 Introduction
This problem has been at the very center of the thinking of the twentieth century. And it will be worthwhile here to briefly look at some of the solutions that have been proposed. I shall mention the eight that I think are most important.
Consciousness as a Property of Matter
The most extensive possible solution is attractive mostly to physicists. It states that the succession of subjective states that we feel in introspection has a continuity that stretches all the way back through phylogenetic evolution and beyond into a fundamental property of interacting matter. The relationship of consciousness to what we are conscious of is not fundamentally different from the relationship of a tree to the ground in which it is rooted, or even of the gravitational relationship between two celestial bodies. This view was conspicuous in the first quarter of this century. What Alexander called compresence or Whitehead called prehension provided the groundwork of a monism that moved on into a flourishing school called Neo-Realism. If a piece of chalk is dropped on the lecture table, that interaction of chalk and table is different only in complexity from the perceptions and knowledges that fill our minds. The chalk knows the table just as the table knows the chalk. That is why the chalk stops at the table.
This is something of a caricature of a very subtly worked out position, but it nevertheless reveals that this difficult theory is answering quite the wrong question. We are not trying to explain how we interact with our environment, but rather the particular experience that we have in introspecting. The attractiveness of this kind of neo-realism was really a part of an historical epoch when the astonishing successes of particle physics were being talked of everywhere. The solidity of matter was being dissolved into mere mathematical relationships in space, and this seemed like the same unphysical quality as the relationship of individuals conscious of each other.
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Consciousness as a Property of Protoplasm
The next most extensive solution asserts that consciousness is not in matter per se; rather it is the fundamental property of all living things. It is the very irritability of the smallest one-celled animals that has had a continuous and glorious evolution up through coelenterates, the protochordates, fish, amphibians, reptiles, and mammals to man.
A wide variety of nineteenth- and twentieth-century scientists, including Charles Darwin and E. B. Titchener, found this thesis unquestionable, initiating in the first part of this century a great deal of excellent observation of lower organisms. The search for rudimentary consciousnesses was on. Books with titles such as The Animal Mind or The Psychic Life of Micro-Organisms were eagerly written and eagerly read.4 And anyone who observes amoebas hunting food or responding to various stimuli, or paramecia avoiding obstacles or conjugating, will know the almost passionate temptation to apply human categories to such behavior.
And this brings us to a very important part of the problem —
our sympathy and identification with other living things. Whatever conclusions we may hold on the matter, it is certainly a part of our consciousness to ‘see’ into the consciousness of others, to identify with our friends and families so as to imagine what they are thinking and feeling. And so if animals are behaving such as we would in similar situations, so well are we trained in our human sympathies that it requires a particular vigor of mind to suppress such identifications when they are not warranted. The explanation for our imputing consciousness to protozoa is simply that we make this common and misleading identification. Yet the explanation for their behavior resides entirely in physical chemistry, not in introspective psychology.
Even in animals with synaptic nervous systems, the tendency 4 By Margaret Floy Washburn, a Titchenerian, and by Alfred Binet respectively.
The real classic in the field of early evolved animals is H. S. Jennings, Behavior of the Lower Organisms (New York: Macmillan, 1906).
6
Introduction
to read consciousness into their behavior comes more from ourselves than from our observations. Most people will identify with a struggling worm. But as every boy who has baited a fish hook knows, if a worm is cut in two, the front half with its primitive brain seems not to mind as much as the back half, which writhes in ‘agony’.5 But surely if the worm felt pain as we do, surely it would be the part with the brain that would do the agonizing.
The agony of the tail end is our agony, not the worm’s; its writhing is a mechanical release phenomenon, the motor nerves in the tail end firing in volleys at being disconnected from their normal inhibition by the cephalic ganglion.
Consciousness as Learning
To make consciousness coextensive with protoplasm leads, of course, to a discussion of the criterion by which consciousness can be inferred. And hence a third solution, which states that consciousness began not with matter, nor at the beginning of animal life, but at some specific time after life had evolved. It seemed obvious to almost all the active investigators of the subject that the criterion of when and where in evolution consciousness began was the appearance of associative memory or learning. If an animal could modify its behavior on the basis of its experience, it must be having an experience; it must be conscious. Thus, if one wished to study the evolution of consciousness, one simply studied the evolution of learning.
This was indeed how I began my search for the origin of consciousness. My first experimental work was a youthful attempt to produce signal learning (or a conditional response) in an especially long suffering mimosa plant. The signal was an intense light; the response was the drooping of a leaf to a care-5 Since an earthworm ‘writhes’ from the tactile stimulation of simply being handled, the experiment is best performed with a razor blade as the worm is crawling over some hard ground or a board. The unbelieving and squeamish may suppress their anguish with the consciousness that they are helping the worm population (and therefore the robin population) since both ends regenerate.
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fully calibrated tactile stimulus where it joined the stem. After over a thousand pairings of the light and the tactile stimulus, my patient plant was as green as ever. It was not conscious.
That expected failure behind me, I moved on to protozoa, delicately running individual paramecia in a T-maze engraved in wax on black Bakelite, using direct current shock to punish the animal and spin it around if it went to the incorrect side. If paramecia could learn, I felt they had to be conscious. Moreover I was extremely interested in what would happen to the learning (and the consciousness) when the animal divided. A first suggestion of positive results was not borne out in later replications.