Criticisms of phenomenalism have tended to be technical. Generally speaking, realists have objected to it on the ground that it is counterintuitive to think of physical objects such as tomatoes as being sets of actual or possible perceptual experiences. Realists argue that one does have such experiences, or under certain circumstances would have them, because there is an object out there that exists independently and is their source. Phenomenalism, they contend, implies that if no perceivers existed, then the world would contain no objects, and that is surely inconsistent both with what ordinary persons believe and with the known scientific fact that all sorts of objects existed in the universe long before there were any perceivers. But supporters deny that phenomenalism carries such an implication, and the debate about its merits remains unresolved. Later analytic epistemology
Beginning in the last quarter of the 20th century, important contributions to epistemology were made by researchers in neuroscience, psychology, artificial intelligence, and computer science. Those investigations produced insights into the nature of vision, the formation of mental representations of the external world, and the storage and retrieval of information in memory, among many other processes. The new approaches, in effect, revived theories of indirect perception that emphasized the subjective experience of the observer. Indeed, many such theories made use of concepts—such as “qualia” and “felt sensation”—that were essentially equivalent to the notion of sense-data.
Some of the new approaches also seemed to lend support to skeptical conclusions of the sort that early sense-data theorists had attempted to overcome. The neurologist Richard Gregory (1923–2010), for example, argued in 1993 that no theory of direct perception, such as that proposed by Gibson, could be supported, given
the indirectness imposed by the many physiological steps or stages of visual and other sensory perception.…For these and other reasons we may safely abandon direct accounts of perception in favor of indirectly related and never certain…hypotheses of reality.
Similarly, work by another neurologist, Vilayanur Ramachandran (born 1951), showed that the stimulation of certain areas of the brain in normal people produces sensations comparable to those felt in so-called “phantom limb” phenomena (the experience by an amputee of pains or other sensations that seem to be located in a missing limb). The conclusion that Ramachandran drew from his work is a modern variation of Descartes’s “evil genius” hypothesis: that we can never be certain that the sensations we experience accurately reflect an external reality.
On the basis of such experimental findings, many philosophers adopted forms of radical skepticism. Benson Mates (1919–2009), for example, declared:
Ultimately the only basis I can have for a claim to know that there exists something other than my own perceptions is the nature of those very perceptions. But they could be just as they are even if there did not exist anything else. Ergo, I have no basis for the knowledge-claim in question.
Mates concluded, following Sextus Empiricus (flourished 3rd century ce), that human beings cannot make any justifiable assertions about anything other than their own sense experiences.
Philosophers have responded to such challenges in a variety of ways. Avrum Stroll (1921–2013), for example, argued that the views of skeptics such as Mates, as well those of many other modern proponents of indirect perception, rest on a conceptual mistake: the failure to distinguish between scientific and philosophical accounts of the connection between sense experience and objects in the external world. In the case of vision, the scientific account (or, as he called it, the “causal story”) describes the familiar sequence of events that occurs according to well-known optical and physical laws. Citing that account, proponents of indirect perception point out that every event in such a causal sequence results in some modification of the input it receives from the preceding event. Thus, the light energy that strikes the retina is converted to electrochemical energy by the rods and cones, among other nerve cells, and the electrical impulses transmitted along the nervous pathways leading to the brain are reorganized in important ways at every synapse. From the fact that the input to every event in the sequence undergoes some modification, it follows that the end result of the process, the visual representation of the external object, must differ considerably from the elements of the original input, including the object itself. From that observation, theorists of indirect perception who are inclined toward skepticism conclude that one cannot be certain that the sensation one experiences in seeing a particular object represents the object as it really is.
But the last inference is unwarranted, according to Stroll. What the argument shows is only that the visual representation of the object and the object itself are different (a fact that hardly needs pointing out). It does not show that one cannot be certain whether the representation is accurate. Indeed, a strong argument can be made to show that human perceptual experiences cannot all be inaccurate, or “modified,” in this way, for if they were, then it would be impossible to compare any given perception with its object in order to determine whether the sensation represented the object accurately, but in that case it also would be impossible to verify the claim that all our perceptions are inaccurate. Hence, the claim that all our perceptions are inaccurate is scientifically untestable. According to Stroll, that is a decisive objection against the skeptical position.
The implications of such developments in the cognitive sciences are clearly important for epistemology. The experimental evidence adduced for indirect perception has raised philosophical discussion of the nature of human perception to a new level. It is clear that a serious debate has begun, and at this point it is impossible to predict its outcome. Avrum Stroll
Citation Information
Article Title: Epistemology
Website Name: Encyclopaedia Britannica
Publisher: Encyclopaedia Britannica, Inc.
Date Published: 02 May 2019
URL: https://www.britannica.com/topic/epistemology
Access Date: August 16, 2019
Additional Reading General works
The texts of classic works in epistemology are available in many English-language translations; two notable collections are The Loeb Classical Library and the Oxford Classical Text series. Ancient epistemology
An excellent collection on skepticism is Myles Burnyeat (ed.), The Skeptical Tradition (1983). Greek Skepticism in particular is covered in R.J. Hankinson, The Sceptics (1999). Medieval epistemology
For the period as a whole, of interest are appropriate articles in The Cambridge History of Later Greek and Early Medieval Philosophy, ed. by A.H. Armstrong (1967); and The Cambridge History of Later Medieval Philosophy: From the Rediscovery of Aristotle to the Disintegration of Scholasticism, 1100–1600, ed. by Norman Kretzmann, Anthony Kenny, and Jan Pinborg (1982). Modern epistemology
Two excellent and now classic histories of early modern philosophy from different perspectives are Edwin Arthur Burtt, The Metaphysical Foundations of Modern Physical Science, rev. ed. (1972), which emphasizes the effect of modern science on philosophy; and Richard H. Popkin, The History of Scepticism from Erasmus to Spinoza, rev. and expanded ed. (1979; also published as The History of Scepticism: From Savonarola to Bayle, 2002), which emphasizes the rediscovery of skepticism in the 16th century.