 There are three questions raised by the title of this entry. The first is whether it is anachronistic. Is empiricism not a modern position? Can we attribute it to ancient and medieval thinkers? The charge of anachronism would, perhaps, be warranted if empiricism referred to a single set of beliefs. As we shall see, however, the term covers a variety of views regarding knowledge  (sect. 2).  Even among modern thinkers, the empiricism of John Locke (1632–1704) is not identical with that of Francis Bacon (1561–1626), and neither bears much resemblance to the empiricism of Rudolf Carnap (1891–1970), A. J. Ayer (1910–1989), or Hans Reichenbach (1891–1953). Yet all these thinkers have an attitude in common: they share a desire to keep factual claims (in the sense of claims regarding contingent matters) closely related to the deliverances of the senses. That desire has ancient roots. Modern empiricism was not a creatio e nihilo. It represented a revival of attitudes found already in the ancient world and the form in which it was expressed was dependent on late medieval developments.