This identification of the complex machinery of human perception with that of animals must not be regarded as an absurd paradox, since, as we have shown in an earlier work, they were originally and in themselves the same.[8] By pursuing an easy mode of observation, divested of prejudice, we may revert to that primeval state of human nature, and may also comprehend with truth and certainty the condition of animals. For the animal nature has not ceased to exist in man, and it may be discerned by those who care to look for it; and careful study, with the constant aid of observation and experiment, will reveal to us the hidden life of sensation and intelligence in the lower animals.
There is a continual self-consciousness in all animals; it is inseparable from all their internal and external acts, from every fact, passion, and emotion; and this is clear and obvious. This fundamental and persistent self-consciousness--persistent in dreams, and even in the calmest sleep, which is always accompanied by a vague sensation--is the consciousness of a living subject, active, impressionable, exercising his will, capable of emotions and passions. It is not the consciousness of an inert thing, passive, dead, or extrinsic; for animal life consists in sensation of greater or less intensity, but always of sensation. Consequently, such a consciousness signifies for the animal a constant apprehension of an active faculty exercised intrinsically in himself, and it makes his life into a mobile drama, of which he is implicitly conscious, of acts and emotions, of impulses, desires, and suspicions.
This inward form of emotional life and psychical and organic action, into which the whole value of personal existence is resolved, may be said to invest and modify all the animal's active relations to the external world, which it vivifies and modifies according to its own image. The subsequent act of doubling the faculties which takes place in man does not occur in the animal; a process which modifies through the intellect the spontaneous and primitive act. Consequently, the active and inward sense which is peculiar to the animal is renewed in him by the external things and phenomena of nature which stimulate and excite him.