100. Several singular positions which have led to an undue depreciation of Descartes in general as a philosopher, occur in his metaphysical writings. Such was his denial of thought, and, as is commonly said, sensation to brutes, which he seems to have founded on the mechanism of the bodily organs, a cause sufficient, in his opinion, to explain all the phænomena of the motions of animals, and to obviate the difficulty of assigning to them immaterial souls;[247] his rejection of final causes in the explanation of nature, as far above our comprehension, and unnecessary to those who had the internal proof of God’s existence; his still more paradoxical tenet that the truth of geometrical theorems, and every other axiom of intuitive certainty, depended upon the will of God; a notion that seems to be a relic of his original scepticism, but which he pertinaciously defends throughout his letters.[248] From remarkable errors, men of original and independent genius are rarely exempt; Descartes had pulled down an edifice constructed by the labours of near two thousand years, with great reason in many respects, yet perhaps with too unlimited a disregard of his predecessors; it was his destiny, as it had been theirs, to be sometimes refuted and depreciated in his turn. But the single fact of his having first established, both in philosophical and popular belief, the immateriality of the soul, were we even to forget the other great accessions which he made to psychology, would declare the influence he has had on human opinion. From this immateriality, however, he did not derive the tenet of its immortality. He was justly contented to say that from the intrinsic difference between mind and body, the dissolution of the one could not necessarily take away the existence of the other, but that it was for God to determine whether it should continue to exist; and this determination, as he thought, could only be learned from his revealed will. The more powerful arguments, according to general apprehension, which reason affords for the sentient being of the soul after death, did not belong to the metaphysical philosophy of Descartes, and would never have been very satisfactory to his mind. He says, in one of his letters, that “laying aside what faith assures us of, he owns that it is more easy to make conjectures for our own advantage and entertain promising hopes, than to feel any confidence in their accomplishment.”[249]