Columbia subject headings:
Perry, Ralph Barton, 1876-1957.
Realism.
Santayana, George, 1863-1952.
Thomas, Aquinas, Saint, 1225?-1274--Philosophy.
Harvard subject headings:
Perry, Ralph Barton, 1876-1957
Realism
Santayana, George, 1863-1952
Thomas, Aquinas, Saint, 1225?-1274--Philosophy.
Princeton subject headings: