Anderson’s ontology was theory of situations existing in space-time. Anderson called this theory ‘empiricism’ which has led to confusion with the ‘empiricism’ of Locke, Berkeley and Hume. For Anderson, British Empiricism was a variation of Idealism and hence to be rejected. His use of empiricism was derived from the Australian philosopher Samuel Alexander who used the term to refer to an ‘empiricist’ (as distinct from a ‘rationalist’) theory of existence.

Anderson’s theory of Space-Time should also be distinguished from Einstein’s relativistic theory of space-time. For Anderson, relativity theory commits the error of treating Space-Time as a thing, whereas on his own view Space-Time is a medium in which things exist.

Apart from a theory of Space-Time, Anderson also developed an extensive theory of categories based on the earlier work of Alexander.

Anderson’s empiricism was a development of his view of Realism. If no thing is constituted by the relations that it has, then the spatio-temporal relations between objects are as real as the objects themselves.