Such was the opinion of Gassendi, as we find in his objections to Descartes. "It is true," says Gassendi, "that you know that you think; but you, who think, know not of what kind of substance you are. Thus, though the operation of thought is known to you, the principle of your essence is hidden from you, and you do not know what is the nature of that substance, one of the operations of which is to think. You resemble a blind man who, feeling the heat of the sun, and being informed that it is caused by the sun, should believe himself to have a clear and distinct idea of that luminary, because, if he were asked what the sun is, he could answer, that it is a thing which warms...." The same Gassendi, in his "Philosophy of Epicurus," repeats several times that there is no mathematical evidence of the pure spirituality of the soul. Descartes, in one of his letters to Elizabeth, princess palatine, says to her: "I confess, that by natural reason alone, we can form many conjectures about the soul, and conceive flattering hopes; but we can have no assurance." And here Descartes combats in his letters what he advances in his books--a too ordinary contradiction. We have seen, too, that all the fathers in the first ages of the Church, while they believed the soul immortal, believed it to be material. They thought it as easy for God to preserve as to create. They said, God made it thinking, He will preserve it thinking. Malebranche has clearly proved, that by ourselves we have no idea, and that objects are incapable of giving us any; whence he concludes that we see all things in God. This, in substance, is the same as making God the author of all our ideas; for wherewith should we see ourselves in Him, if we had not instruments for seeing? and these instruments are held and directed by him alone. This system is a labyrinth, of which one path would lead you to Spinozism, another to Stoicism, another to chaos. When men have disputed well and long on matter and spirit, they always end in understanding neither one another nor themselves. No philosopher has ever been able to lift by his own strength the veil which nature has spread over the first principle of things. They dispute, while nature is acting. SECTION III. _On the Souls of Beasts, and on Some Empty Ideas._ Before the strange system which supposes animals to be pure machines without any sensation, men had never imagined an immaterial soul in beasts; and no one had carried temerity so far as to say that an oyster has a spiritual soul. All the world peaceably agreed that beasts had received from God feeling, memory, ideas, but not a pure spirit. No one had abused the gift of reason so far as to say that nature has given to beasts the organs of feeling, in order that they may have no feeling. No one had said that they cry out when wounded, and fly when pursued, without experiencing either pain or fear.