KARL POPPER Biography Sir Karl Popper , in full Karl Raimund Popper born July 28, 1902 , Vienna , Austria , died Sept. 17, 1994 , Croydon , Greater London , Austrian-born British philosopher of natural and social science who subscribed to antideterminist metaphysics , believing that knowledge evolves from experience of the mind . Philosophy Popper coined the term "critical rationalism" to describe his philosophy. Concerning the method of science, the term indicates his rejection of classical empiricism , and the classical observationalist-inductivist account of science that had grown out of it. Popper argued strongly against the latter, holding that scientific theories are abstract in nature, and can be tested only indirectly, by reference to their implications. He also held that scientific theory, and human knowledge generally, is irreducibly conjec...