"Very ingeniously Lamettrie observes that at bottom I am immediately certain only of my own feeling. That other men also feel, I conclude with very much stronger conviction from the expression of their feelings in gestures and cries than from their articulate speech. That energetic language of the emotions is, however, the same in the animals as in men, and it carries with it much stronger proof than all the sophisms of Descartes. ...[T]he internal organisation of man and of the animals offers a perfect analogy. If it remains for the present incomprehensible how the capability of feeling can be an attribute of matter, it is with this, as with a thousand other puzzles, in which, according to an idea of Leibniz, instead of the thing itself we see only the veil that hides it. ...[S]ensation, like motion, must at all events potentially belong to all matter. So thought the ancients, whose philosophy is preferred by all capable minds to the inadequate attempts of the moderns. After this Lamettrie passes to the doctrine of substantial forms..."