Putnam's Paradox is a philosophical problem that arises in the context of reference theory and meaning. It suggests that if we consider the meaning of a term to be determined by the objects it refers to, then the meaning of a term can change based on the context. For example, the term "water" refers to H2O, but in a different context, it could refer to a different substance that shares similar properties. This paradox highlights the tension between externalism and internalism in understanding meaning. Externalism posits that the meaning of a term is influenced by external factors, while internalism argues that meaning is determined solely by mental states. Putnam's Paradox challenges us to think about how context and reference shape our understanding of language and meaning.