Effluxes, Theory of
(Lat. efflux, from effluere, to flow out) Theory of early Greek thinkers that perception is mediated by effluvia or simulacra projected by physical objects and impinging upon the organs of sense. Thus Empedocles developed the theory of effluxes in conjunction with the principle that “like perceives only like” (similia similibus percipiuntur); an element in the external world can only be perceived by the same element in the body. (See Aristotle, De Gen. et Corr. I, 8, 324b26; Theophrastus, De Sens. 7.) Democritus’ theory of images is a form of the theory of effluxes. — L.W.