"We have now but to prove a third attribute: I mean the faculty of feeling which the philosophers of all centuries have found in this same substance. ...[T]he Cartesians have made, in vain, to rob matter of this faculty. But in order to avoid insurmountable difficulties, they have flung themselves into a labyrinth from which they have thought to escape by this absurd system "that animals are pure machines." An opinion so absurd has never gained admittance among philosophers... Experience gives us no less proof of the faculty of feeling in animals than of feeling in men."