Born in Czechoslovakia, Ernest Nagel (1901–1985) lived in the United States after 1910 and was a member of the Columbia University philosophy department for over 40 years. His The Structure of Science (1961) is probably the last important logical positivist account of scientific investigation. Nagel extended the principles of the “covering law model,” whereby explanation is based on a generalization that has been inductively built up, for the social sciences. He argued that although historical events are unique and non-recurring, historical explanation implies that such events would happen again, given the same conditions and proven generalizations.