PHENOMENALISM, in philosophy, is a name applied to several different schools of thought which maintain in common that human knowledge (so-called) is confined to phenomena in the broad sense of the term, according to which it denotes gen erally events or things in space and time. But the schools differ among themselves on the ontological (as distinguished from the epistemological) question relating to the objective source or basis of the phenomena. (I) According to one view it is assumed more or less that there is an objective reality of which the phenom ena are the changing appearances, but it is maintained that this ultimate basic reality is beyond the reach of human knowledge, which is limited to the apprehension of appearances adapted to or relative to human powers. In one form or another some such view is maintained by Agnosticism, the critical Philosophy, Empiricism, and Positivism.
(2) Another view is to the effect that there is no permanent substance underlying the ever-changing flux of phenomena ; in other words, these ever-changing phenomena are the only reality.
This was the view held by Heraclitus among the ancient Greeks, and by Bergson among present-day philosophers, also by others.
(3) Yet a third view would deny the external existence even of phenomena in the ordinary sense of the term (that is, events actually occurring in space and time) and identifies all reality with the mere appearances to or in the mind or mental experi ences as such. This view is represented by Shadworth Hodgson, the author of The Metaphysic of Experience (1898), and others.
It should be observed that the first kind of phenomenalism (I) is merely epistemological, whereas the other two, (2) and (3), are also ontological. Ontological phenomenalism implies epistemological phenomenalism, but not vice versa. See META PHYSICS, and KNOWLEDGE, THEORY OF.