who introduced the brain-in-a-vat scenario into philosophy? my best candidate is jonathan harrison's wonderful and under-recognized 1967 story "a philosopher's nightmare" (jstor.org/stable/4544744), about a subject whose brain is in an "endocephalic electrohallucinator" and who goes on to read great philosophers on skepticism and declares that the external world exists. of course there are many related antecedents in philosophy (descartes, zhuangzi, etc), as well as in science fiction (see e.g. sf-encyclopedia.com/entry/br…) and biology (e.g. en.wikipedia.org/wiki/Isolat…). but harrison is the first that i know of to make a sustained connection between brains in vats and skepticism about the external world. (earlier references are welcome!) here's a marvelous illustration of harrison's story by @timothypeacock from my book reality+.