Conversation so far:
What is Epistemology?
In the field of epistemology, Putnam is known for his "brain in a vat" thought experiment (a modernized version of Descartes's evil demon hypothesis).

Question: What was Putnam's "brain in a vat" experiment?
Self-contained rewrite: What was Hilary Putnam's "brain in a vat" experiment in the field of epistemology?