Descartes's Real Argument

It is still commonly supposed that Descartes based his argument for the mind-body distinction on the law of the indiscernibility of identicals. I argue that this interpretation is very unlikely to be correct. I explain three contemporary versions of this interpretation and say why I reject it. Basically, use of this law for Descartes's conclusion would require reference to human bodies or else the supposition, for the purpose of the argument, of reference to human bodies. But at the time Descartes formulated his argument, he would not have allowed either. Instead, I amend a different interpretation which others have found, and briefly defend it against one famous objection.