This is the 2011 Aquinas Lecture delivered by John McDowell on February 27, 2011 at Marquette University. A central theme in much of Professor McDowell's work is the harmful effect, in modern philosophy and in the modern reception of pre-modern philosophy, of a conception of nature that reflects an understanding, in itself perfectly correct, of the proper goals of the natural sciences. He has argued that we can free ourselves from the characteristic sorts of philosophical anxiety by recalling the possibility of a less restrictive conception of what it takes for something to be natural.