(AT 3:500; CSMK, 207) Descartes goes on to suggest several arguments that Regius might make against substantial forms, but this passage illustrates the heart of his view: substantial forms are not needed, hence should not be made use of, hence are in effect rejected.
(AT 3:506; CSMK, 208-9) Rather than appealing to the explanatory power of his own account, Descalles now shifts his focus to the worthlessness of scholastic accounts.
In his correspondence with Regius, he writes that the soul is "the true substantial form of man" (AT 3:505; CSMK, 208).
1641), that "when we consider the body alone we evidently perceive nothing in it demanding union with the soul" (AT 3:461; CSMK, 200).
"And so, even though that matter changes, and its quantity increases or decreases, we still believe that it is the same body, numerically the same body, so long as it remains joined and substantially united with the same soul" (AT 4:166; CSMK, 243).
"I would also like to know whether there is someone who has written a summary of all of scholastic philosophy and who has a following, for this would spare me the time to read their big books" (AT 3:185; CSMK, 154).
"are harder to understand than all the things they are supposed explain." For further disparaging remarks, see CSMK, 107, 122, 188, 221; AT 8B:26; AT 1:430.
(39) See AT 8B:351 (CSM 1:299); AT 3:460 (CSMK, 200).
(40) See, for example, his exchange with Arnauld on whether a sheep can see a wolf and run away without a rational soul (AT 7:205, 230, CSM 2:144, 161), as well as AT 11:202 (CSM 1:108), AT 1:414-15 (CSMK, 62), and AT 2:40-41 (CSMK, 99-100).
(41) Earlier in this same letter, Descartes remarks that "the human soul alone is recognized as a substantial form, whereas other forms consist in the configuration and motion of their parts" (AT 3:503; CSMK, 207).