brain in a vat: a standalone construct

Hilary Putnam presented the brain in a vat in the first chapter of Reason, Truth and History (1981): imagine your brain removed from your body and kept alive in a vat of nutrients, wired to a computer that feeds it electrical signals producing exactly the experiences you now have, so that from the inside nothing would seem different and you could not tell you were such a brain. The setup reworks Descartes's 1641 evil-demon doubt, the worry that an all-powerful deceiver might be feeding you a false world, into a physical, neuroscientific form, and it raises the question of how anyone can know they are not already a brain in a vat. Putnam himself used it to argue the reverse of the skeptic's conclusion: on a theory of meaning called semantic externalism, in which what a word refers to depends partly on the things a speaker has actually been in contact with, a lifelong brain in a vat could not even truly think the thought "I am a brain in a vat," so the hypothesis is self-refuting. Anthony Brueckner's paper Brains in a Vat (1986) gave the standard reconstruction of this self-refutation argument and set the terms for the debate that followed. The construct is distinctive as the modern reference case for radical skepticism about the external world, a single vivid scenario that recurs across epistemology, philosophy of mind, and philosophy of language to test what knowledge, reference, and perception require.[1][2][3]

Unit

A philosophical thought experiment: one hypothetical scenario used to probe a claim about knowledge and meaning

Recovery means

Not applicable

Measured by

Not measured empirically; stated as a hypothetical scenario and assessed by philosophical analysis of its coherence and of what conclusions do or do not follow from it