In 1975, Hilary Putnam published the article "The Meaning of "Meaning"" in which he proposed the doctrine that became known as semantic externalism. His idea was that the meaning of words cannot be established by an individual in isolation (or by mind taken in isolation). In this work, we investigate Putnam"s thesis from several different perspectives, aiming at giving the reader elements to understand it in detail. These perspectives include the precise definition of semantic externalism, the arguments Putnam uses to support it, and the investigation of some consequences of the doctrine for the philosophy of language, the philosophy of science, and the philosophy of mind.