Subjectivism is the philosophical tenet that "our own mental activity is the only unquestionable fact of our experience". In other words, subjectivism is the doctrine that knowledge is merely subjective and that there is no external or objective truth. The success of this position is historically attributed to Descartes and his methodic doubt. Subjectivism accords primacy to subjective experience as fundamental of all measure and law. In extreme forms like Solipsism, it may hold that the nature and existence of every object depends solely on someone's subjective awareness of it. One may consider the qualified empiricism of George Berkeley in this context, given his reliance on God as the prime mover of human perception. Thus, subjectivism.