In metaphysics, phenomenalism asserts that physical objects do not possess an independent existence as "things-in-themselves," but rather manifest solely as perceptual phenomena or sensory stimuli (e.g., redness, hardness, softness, sweetness) apprehended within spatiotemporal frameworks. Specifically, certain phenomenalist perspectives interpret all discourse concerning external physical objects as reducible to discussions of bundles of sense data.
Historical Context
Phenomenalism represents a stringent empirical doctrine. Its ontological foundations, concerning the nature of existence, originate with George Berkeley's subjective idealism, a concept subsequently refined by David Hume. John Stuart Mill developed a theory of perception, widely recognized as classical phenomenalism. A key distinction from Berkeley's idealism lies in Mill's explanation of object persistence in the absence of perception. Berkeley posited that an omniscient deity's continuous perception sustained the existence of all objects, while Mill contended that permanent possibilities of experience adequately accounted for an object's continued being. Such permanent possibilities were amenable to analysis as counterfactual conditionals, exemplified by statements like: "if I were to experience y-type sensations, then I would concurrently experience x-type sensations."
Conversely, as an epistemological framework addressing the potential for knowledge regarding external objects, phenomenalism finds its most comprehensible articulation within Immanuel Kant's transcendental idealism. Kant asserted that space and time, functioning as the a priori forms and fundamental preconditions of all sensory experience, "pertain to objects exclusively insofar as these are conceptualized as phenomena, rather than representing things-in-themselves." Although Kant maintained that knowledge is confined to phenomena, he neither repudiated nor precluded the existence of objects inaccessible through empirical experience—namely, things-in-themselves or noumena. Nevertheless, his substantiation of noumena presented numerous challenges and remains among the most contentious elements of his Critiques.
Consequently, Kant's "epistemological phenomenalism," as it is designated, diverges significantly from Berkeley's preceding ontological interpretation. Berkeley contended that "things-in-themselves" exist solely as subjectively perceived aggregates of sensations, whose consistency and permanence are ensured by their perpetual apprehension within the divine mind. Thus, while Berkeley posits that objects are simply collections of sensations, Kant (in contrast to other bundle theorists) maintains that objects persist even when they are not being perceived by a merely human subject or consciousness.
During the late 19th century, Ernst Mach articulated a more radical iteration of phenomenalism, subsequently elaborated and refined by Russell, Ayer, and the logical positivists. Mach repudiated the concept of God's existence and furthermore disavowed the notion that phenomena constituted data experienced by subjects' minds or consciousnesses. Instead, Mach posited sensory phenomena as "pure data," whose existence predated any arbitrary categorization into mental or physical domains. Thus, Mach established the central tenet of phenomenalism, distinguishing it from object bundle theories: phenomenalism asserts that objects are logical constructions derived from sense-data or ideas, whereas bundle theories contend that objects comprise sets or aggregates of actual ideas or perceptions.
Specifically, within bundle theory, asserting the existence of a pear signifies merely that particular properties (e.g., greenness, hardness) are presently being perceived. Should these characteristics cease to be perceived or experienced by any observer, the object (in this instance, the pear) consequently ceases to exist. In contrast, Mach's formulation of phenomenalism posits that objects constitute logical constructions derived from perceptual properties. From this perspective, stating that a table exists in an unoccupied room implies that if an individual were present in that room, then that person would perceive the table. The emphasis is not on actual perception, but rather on the conditional possibility of perception.
Logical positivism, originating from a small intellectual circle formed around philosopher Moritz Schlick in Vienna, significantly influenced numerous philosophers in the Anglophone world between the 1930s and 1950s. Key figures shaping this empirical tradition included Ernst Mach, who held the Chair of Inductive Sciences at the University of Vienna—a position later occupied by Schlick—and the Cambridge philosopher Bertrand Russell. Prominent logical positivists, including A. J. Ayer and Rudolf Carnap, sought to implement phenomenalism linguistically, thereby facilitating precise discussions of physical entities, such as tables, exclusively through the lens of actual or potential sensory experiences.
Arthur Danto, an American philosopher of the 20th century, posited that "a phenomenalist, believ[es] that whatever is finally meaningful can be expressed in terms of our own [sense] experience." He further contended that "The phenomenalist really is committed to the most radical kind of empiricism: For him reference to objects is always finally a reference to sense-experience ... ."
Building upon George Berkeley's foundational work, Colin Murray Turbayne, a 20th-century Australian philosopher, advocated for a strong version of phenomenalism. He achieved this by proposing a "language model" as a substitute for the prevalent "geometric model," which underpins both contemporary theories of visual perception and classical mechanical philosophy.
For a phenomenalist, all objects must inherently relate to experience. John Stuart Mill famously characterized physical objects as merely the 'permanent possibility of experience,' a concept largely adopted by phenomenalists. Consequently, any discussion of physical—or potentially nonphysical—objects is understood to refer solely to the experiences one would encounter when interacting with them. Nevertheless, phenomenalism fundamentally relies on mental operations that are not themselves derived from sensory experience. These non-empirical, non-sensual operations encompass "...nonempirical matters of space, time, and continuity that empiricism in all its forms and despite its structures seems to require ... ."
Criticisms
Criticisms
C.I. Lewis previously proposed that the assertion "There is a doorknob in front of me" inherently implies the sensory conditional: "If I were to perceive a doorknob and simultaneously initiate a grasping motion, then it is highly probable that the sensation of touching a doorknob would ensue."
In 1950, Roderick Firth presented an additional critique derived from the concept of perceptual relativity. For instance, white wallpaper appears white under white illumination but red under red illumination. Consequently, any potential sequence of experiences resulting from a given action would seemingly fail to definitively specify our environment. It would, for example, only establish that there is either white wallpaper under red light or red wallpaper under white light, among other ambiguities.
Phenomenalism also faces criticism from truthmaker theory, which posits that truth is contingent upon reality. According to this framework, a truthbearer (e.g., a proposition) is true due to the existence of its corresponding truthmaker (e.g., a fact). Phenomenalists have been charged with contravening this principle, engaging in what is termed "ontological cheating" by asserting truths without adequately identifying their truthmakers. This critique primarily targets the phenomenalist explanation of material objects, specifically addressing the challenge of accounting for unperceived material objects. John Stuart Mill offered a notable resolution, proposing that unperceived objects can be explained through counterfactual conditionals: for instance, valuables in a locked safe persist unperceived because if an observer were to look inside, they would experience a corresponding sensory impression. However, truthmaker theorists may counter that this solution still fails to clarify the truthmaker for such a counterfactual conditional, questioning how such a truthmaker could be integrated into a phenomenalist ontology.
Notable proponents
- Johannes Nikolaus Tetens
- John Foster
- Colin Murray Turbayne
- Peripatetic axiom – Philosophical principle quoted by Thomas Aquinas
References
Bibliography
- Phenomenalism in The Garzanti Encyclopedia of Philosophy, edited by Gianni Vattimo and Gaetano Chiurazzi. Third Edition. Garzanti, Milan, 2004. ISBN 88-11-50515-1.
- Berlin, Isaiah. The Refutation of Phenomenalism. The Isaiah Berlin Virtual Library, 2004.
- Bolender, John. Factual Phenomenalism: A Supervenience Theory, in SORITES Issue #09, April 1998, pp. 16–31.
- Phenomenalism at PhilPapers
- Phenomenalism at the Indiana Philosophy Ontology Project