Perception, as a theory in epistemology deals with the knowledge of the external world as it is presented to the perceiver. According to Humer, there are three elements of Perception; a Perceptual Experience, an object of Perception and a Causal Relationship. In essence perception dwells solely in describing the sensual interaction acquisition as well as the acquisition of knowledge; external world. Do we have an interactive relationship with what is outside of us? If so how does the interaction take place? The interaction takes place in the mind or senses? Is the medium of interaction sufficiently reliable to lay claim to knowledge? Theories of perception try to explain these fundamental questions and more with the aim of solving the seemingly problematic phenomenon of how the perceiver grasps what exists outside of him directly or indirectly. It can be said that illusion and hallucination have contributed to the above stated problem. Sense-datum theory of perception which shall be critically observed in this paper how the theory attempted to necessarily and sufficiently explain the genuine knowledge of reality.
Illusion may be defined as “any perceptual situation in which a physical object is actually perceived, but in which that object perceptually appears other than it really is”. For example water can taste bitter if taken immediately after eating walnuts. A fragrance might smell so strong when after all it is many feet away from you. In these cases it is not necessary that one is deceived into believing that things are other than they are; so illusion in this sense need not involve deception. The perceiver persists something in the world though it may be distorted.
Sense-datum in the case of illusion suggests that they exist independent of an object. The mind processes these datum for perception to take place .One can know that one is experiencing an illusion when it is happening. On the other hand illusion can deliver counter-factuals of reality i.e a mirage thought to be rainfall, a slanted ruler in a cup of water misjudged to be straight etc. nothing other than deceptive form of reality is what it can sometimes present to us. A basic idea of illusion is when one is subject to an illusion, seems to one that something has a quality, H, which the real ordinary object supposedly being perceived does not actually have. Also, when it seems to one that something has a quality, H, then there is something of which one is aware which does have this quality. Furthermore, our normal view about perceiving is- sometimes called “naïve realism” or “direct realism”- is false. By this reason perception cannot be normally what we think it is. Naïve realism states that the world is as directly presented to our senses without any alteration whatsoever. An implication that consequently arises will be that considering the deceptive tendencies of illusion reality is still exactly presented to our perceptibility. This suggests the shortcoming, inadequacy and manifest error of naïve realism in the process of perception.
In Hallucination a perceiver’s senses are distorted in conceptualization so that he perceives sense-datum from a non-existent entity in the external immediate world. But how does one perceives through sense-datum of an object that is not directly immediate? Or it’s the suspective case that sense-datum are necessarily independent of object? It appears that nothing dwells in the world as the sense-datum resides in the perceiver. Experience in hallucination seems like a perception of a real, mind-independent object, but where there is no mind-independent object of the relevant kind being perceived.
Another theory of perception is Phenomenalism. In perception the object is nothing but a bundle or collection of sense-data. At this juncture it might be asked is if there are objects that exists independent of the perceiver. Phenomenalists might say no object is independent of the perceiver. Also, there is no reality over and above a collection of sense data. Our senses can never perceive, for example, a table. It is when we collect the data through our senses our mind processes the them. If peradventure one sees a water pool from afar and he does not see it after he comes closer, the phenomenalist will tell that the senses have not deceived but that the mind-the processor produced the datum wrongly. This claim can be in response to the absolute Cartesian doubt of how reliable knowledge from the sense experience is.
Sense-datum theory holds that perception occurs no less or more than sense data in the brain. In essence, perception is not about the outside world but about the activities of the brain in the body. So the objects of experience are really sense-data. A sense-datum is a causal theory of perception with regards to its operation. The sense-datum in the object in the world causes the one perceiving to know. It is simply mediated, hence indirect, causal relation between external objects we perceive and us: the object produces the mediating colors and shapes that appear in our though of objects. Sense-datum unlike hallucination can be regarded as an indirect representative realism because it conceives perception as a relation in which sense-data represent perceived external or real objects to us. On some conceptions of sense-data, they are copies of those objects: shape for shape, color for color, sound for sound. This is reminiscent of the Lockean Representational thought. John Locke held that sense-datum are copies only of the primary qualities of physical things- solidity, extension (in space), shape, and mobility- not of their secondary qualities above colors, sounds, smells, and tastes. (He took the primary qualities to be objective and of the kind that concern physical science; and he considered the secondary ones to be in a sense subjective, not belonging to physical things but something like representational mental elements that they cause in us. Under sense-datum theory, perception is direct awareness of external reality, and that leads to non-inferential knowledge of reality. Through inference, belief from perception is practically not possible.
Objections To The Sense-Datum Theory of Perception
The sense-data find themselves between the perceivers and the mind-independent objects which we normally take ourselves to perceive and therefore leaves our perceptual, cognitive and epistemic access to the world deeply problematic if not possible. Another implication here is that our perceptual, thinking and epistemic tendencies would seem to be useless and unnecessary since the sense-datum have such potent abilities in perception. In response to this, the indirect realists can claim that sense-data are the medium by which we perceive the mind-independent world.
The sense-datum theory of perception lacks clarity in describing the causal connection between perceptual experience, but be close enough that the object directly causes the experience, but ‘directly’ does not specify what qualifies. With a causal connection supposed to come with a detailed explanation on how a sense-data can possibly cause experience in the perceiver. Is it that the perceiver is naturally packaged to process materials brought in by sense data? or in the datum are inherent special powers to complete the perception of genuine knowledge? The theory didn’t dwell on that properly thereby subtly failing to address the long time philosophical problem of perception.
We would have thought of a good theory that aimed well higher than the naïve realism with the introduction of an entity independent of the mind- the sense-data but there can be only guesses as to describe the nature of these sense-datum. On nature, sense-datum are immaterial and do not occupy space but with inherent qualities they are able to serve as the intermediary between the external world as it is presented and the perceiver. How they are able might however not be made known to our understanding. This is slightly arbitrary.
On the critique of hallucination – If a lion is carved by an artist in the natural museum so well that it looks perfectly like the real drawn one , now no matter how real the carved one may be it cannot be that they are both components in ordinary seeing. Similarly, no matter how much like ordinary experiences hallucinations can seem, it does not follow that the former have all the internal elements (roughly, mental or mind-dependent elements). Hence, the two lions differ in their relational properties.
Sense-datum theory of perception, having done a critical assessment of it emerge to be less plausible even though it is an improvement from the direct form of perception in naïve realism but it still appears to take us farther rather than close to deploying an explanation which covers articulately what goes on between the perceiver and the outside material world. The theory would need adjustment to be able to solve pivotal problems in philosophy such as the problem of Perception.
•Hueme Micheal,Skepticism and The Veil Of Perception, Oxford: Rowman and Littlefield Publishers, Inc. 2001