How does the brain-in-a-vat thought experiment raise doubts about sense experience?

The "brains in a vat" thought experiment raises doubts about sense experience by highlighting the logical possibility that our perceptions of the external world are merely illusions produced by electrical stimulation.12

In this scenario, a person’s brain is kept alive in a vat and connected to a computer that simulates reality. Because our only access to the world is through these sensory experiences, there is a logical gap between our internal perceptions and the actual existence of external objects. Consequently, no amount of sensory evidence can definitively prove that we are not in this state, as any evidence we gather could also be simulated.1

However, philosopher Hilary Putnam argued that this skeptical challenge is self-defeating. He contended that if we were indeed brains in a vat, our language would not refer to real objects but only to computer-generated images. Therefore, the statement "we are brains in a vat" would be false, rendering the hypothesis paradoxical and the skeptic's concerns fundamentally unexpressible.32