Phenomenalism

Phenomenalism is the view in Epistemology and the Philosophy of Perception that physical objects do not exist as things in themselves but only as perceptual phenomena or bundles of sense-data situated in time and in space. A phenomenon is any occurrence that may be perceived through a person's senses or with their mind, and the theory proposes that we cannot experience anything beyond the phenomena of our perceptions.

Phenomenalism, then, derives from the metaphysical view that objects are logical constructions out of perceptual properties. It is not so much the actual perception that counts, however, but the conditional possibility of perceiving, so that even when there is no one in a particular room to perceive a table, it is enough to say that if there were someone in that room, then that person would perceive the table.

Phenomenalism can therefore be considered a radical form of Empiricism or Idealism.

Critics have argued that, in the process of eliminating material objects from language and replacing them with hypothetical propositions about observers and experiences, it seems to commit us to the existence of a whole new class of ontological object altogether, that of sense-data which can exist independently of experience. Others have argued that the supposition of an irreducibly material observer (or potential observer) necessitates the existence of a second observer to observe the first (and a third to observe the second, etc), leading to an infinite regress. Another objection stems from perceptual relativity (e.g. white wallpaper looks white under white light and red under red light), and asks on what basis are we to decide which of the possible hypotheses is the correct one if we are constrained to rely exclusively on senses.

The roots of Phenomenalism as an ontological view of the nature of existence can be traced back to George Berkeley and his Subjective Idealism, which David Hume then further elaborated. Berkeley's beliefs were an early kind of bundle theory (the idea that objects are made up of sets, or bundles, of ideas or perceptions), and that when the characteristics of an object are no longer being perceived or experienced by anyone, then the object effectively no longer exists (although Berkeley argued that God always perceived everything, thus maintaining the existence of objects which were not subject to observation by humans).

The 19th Century empiricist John Stuart Mill developed the first phenomenalist theory of perception (commonly referred to as Classical Phenomenalism), which did not require the intervention of God. He spoke of physical objects as the "permanent possibility of experience".

As a robust epistemological theory, however, Phenomenalism can be traced to the Transcendental Idealism of Immanuel Kant. He insisted that knowledge is limited to phenomena, although he never denied or excluded the existence of objects which were not knowable by way of experience (the "things-in-themselves" or noumena), even if they were not provable.

In the late 19th Century, an even more extreme form of Phenomenalism was formulated by the Bohemian-Austrian philosopher Ernst Mach (1838 - 1916), and later developed and refined by Bertrand Russell, A. J Ayer and the Logical Positivism movement. Sensory phenomena, for Mach, are "pure data" with no need of being experienced by the mind or consciousness of subjects. The logical positivists went on to formulate the doctrine of Phenomenalism in linguistic terms.