Brain in a Vat Argument

A contemporary version of Cartesian skepticism: perhaps we are disembodied brains in vats, connected to a supercomputer that provides all our sensory experiences — making our beliefs about the external world systematically false.

Raises questions about the nature of knowledge, the possibility of global skepticism, and the relationship between semantic content and causal connection to the world. Hilary Putnam argues the scenario is self-refuting: if we were brains in vats, our words would refer to vat-world objects, not real brains and vats.