A philosophical position, empirical in method, that regards everything that exists or occurs to be conditioned in its existence or occurrence by causal factors within one all-encompassing system of nature, however “spiritual” or purposeful or rational some of these things and events may in their functions and values prove to be.

P. Lamprecht in Naturalism and the Human Spirit, Yervant H. Krikorian, 1944, p. 18, quoted in Christian Apologetics in a World Community, W. Dyrness, IVP, 1983, p. 88.