What! that bird which makes its nest in a semi-circle when it is attaching it to a wall, which builds it in a quarter circle when it is in an angle, and in a circle upon a tree; that bird acts always in the same way? That hunting-dog which you have disciplined for three months, does it not know more at the end of this time than it knew before your lessons? Does the canary to which you teach a tune repeat it at once? do you not spend a considerable time in teaching it? have you not seen that it has made a mistake and that it corrects itself?
Is it because I speak to you, that you judge that I have feeling, memory, ideas? Well, I do not speak to you; you see me going home looking disconsolate, seeking a paper anxiously, opening the desk where I remember having shut it, finding it, reading it joyfully. You judge that I have experienced the feeling of distress and that of pleasure, that I have memory and understanding.
Bring the same judgment to bear on this dog which has lost its master, which has sought him on every road with sorrowful cries, which enters the house agitated, uneasy, which goes down the stairs, up the stairs, from room to room, which at last finds in his study the master it loves, and which shows him its joy by its cries of delight, by its leaps, by its caresses.
Barbarians seize this dog, which in friendship surpasses man so prodigiously; they nail it on a table, and they dissect it alive in order to show the mesenteric veins. You discover in it all the same organs of feeling that are in yourself. Answer me, machinist, has nature arranged all the means of feeling in this animal, so that it may not feel? has it nerves in order to be impassible? Do not suppose this impertinent contradiction in nature.
But the schoolmasters ask what the soul of animals is? I do not understand this question. A tree has the faculty of receiving in its fibres its sap which circulates, of unfolding the buds of its leaves and its fruit; will you ask what the soul of this tree is? it has received these gifts; the animal has received those of feeling, of memory, of a certain number of ideas. Who has bestowed these gifts? who has given these faculties? He who has made the grass of the fields to grow, and who makes the earth gravitate toward the sun.
"Animals' souls are substantial forms," said Aristotle, and after Aristotle, the Arab school, and after the Arab school, the angelical school, and after the angelical school, the Sorbonne, and after the Sorbonne, nobody at all.
"Animals' souls are material," cry other philosophers. These have not been in any better fortune than the others. In vain have they been asked what a material soul is; they have to admit that it is matter which has sensation: but what has given it this sensation? It is a material soul, that is to say that it is matter which gives sensation to matter; they cannot issue from this circle.
Listen to other brutes reasoning about the brutes; their soul is a spiritual soul which dies with the body; but what proof have you of it? what idea have you of this spiritual soul, which, in truth, has feeling, memory, and its measure of ideas and ingenuity; but which will never be able to know what a child of six knows? On what ground do you imagine that this being, which is not body, dies with the body? The greatest fools are those who have advanced that this soul is neither body nor spirit. There is a fine system. By spirit we can understand only some unknown thing which is not body. Thus these gentlemen's system comes back to this, that the animals' soul is a substance which is neither body nor something which is not body.
Whence can come so many contradictory errors? From the habit men have always had of examining what a thing is, before knowing if it exists. The clapper, the valve of a bellows, is called in French the "soul" of a bellows. What is this soul? It is a name that I have given to this valve which falls, lets air enter, rises again, and thrusts it through a pipe, when I make the bellows move.
There is not there a distinct soul in the machine: but what makes animals' bellows move? I have already told you, what makes the stars move. The philosopher who said, "Deus est anima brutorum," was right; but he should go further.