Putnam’s goal is to refute the skeptical argument that is based on the BIV hypothesis, by providing a counterargument for the conclusion that we are not BIVs. Thus, each of us is provided with a way of knowing that she is not a BIV, contrary to premise (3) of the skeptical argument (SA) above. The crucial move in Putnam’s argument is a sub-argument to the effect that that if one were a BIV, one would not be able to grasp the meanings of various general terms, such as ‘tree’, ‘brain’, and ‘vat’.