Descartes and other philosophers have held that there is a great difference in the mental processes of animals as compared with those of man in this, namely, that man is "conscious," that is to say, conscious of himself as "I," and, as it were, looks on at himself acting on and being acted on by surrounding existences, whilst (so it is assumed) animals have not this consciousness, but are "automata," going through all the processes of life, and even behaving more or less as man does in similar circumstances, yet without being "conscious." It is, no doubt, true that many of the complicated actions of insects are carried on without consciousness of the purpose or significance of what they are doing. Such is the storing by certain wasps of smaller insects in carefully-cut chambers, to serve as food for the wasp's young, to be hatched from an egg to be laid in the "cold-storage chamber." The mother wasp will go on doing this when she has had the hind part of her body removed and has no eggs to lay. This mechanical unreasoning behaviour in insects is without exception, so that we must accept M. Fabre's conclusion that they are, in fact, unconscious "automata." I have already referred to this subject in an earlier chapter, p. 197. We at once place ourselves in difficulty in discussing this subject by the use of the words "conscious" and "consciousness," for, as so often happens, they are customarily applied in a vague and uncertain way to the mental activities of man--without any precise agreement as to what is meant by either of them. We are all agreed that a rational human being may go through a series of elaborate actions apparently directed by purpose and yet not be what we call "conscious," that is to say, "aware" of what he is doing. This occurs in "sleep-walking" and in "day-dreaming." And again, we know that a man may be evidently conscious during a certain period, and yet forget directly afterwards that he has been conscious and said and done certain things during that period. This often happens after "concussion of the brain." It is, as a matter of fact, uncertain whether one ought to regard the condition of a man during that obliterated or forgotten period of seeming consciousness as rightly to be described by the term "conscious." And the reason why one has this doubt is that we all recognize that consciousness without memory is really a contradiction in terms. Memory--the inscription or record in our brains of past experiences--exists without consciousness, as we all know, by observation of ourselves and our fellows. But the very essence of consciousness is memory. We cannot even be "conscious" of the experience of a single moment without being also conscious of the memory of some previous condition--however small, temporary, and incomplete the memory may be. To be conscious we must _compare_ the impressions reaching the brain at this moment with the memory of those of a past moment. And in lower animals and infants beginning to be