Dr. N.L. Kachhara
Epistemology, or The Theory of Knowledge, is the branch of philosophy concerned with the nature and scope of knowledge and how it relates to similar notions such as truth, belief and justification. It has been argued that epistemology should evaluate peoples' properties (i.e., intellectual virtues) instead of propositional properties. Belief is a subjective, personal basis for an individual's behavior, while truth is an objective statement that is independent of the individual. The terms knowledge and perception in Western philosophy are used almost in the same sense as jnana and darshana, of indirect type, in Jain philosophy although they differ in actual connotation. I here briefly review the Western philosophical views of knowledge and perception. This study indicates the complexity of the phenomena at physical level involved in the process of knowledge, perception, and cognition.
The (classical) definition of knowledge as "justified true belief" was widely accepted until the 1960s. In 1963 Edmund Gettier stated that, while justified belief in a proposition is necessary for that proposition to be known, it is not sufficient. In response to this, revised definitions have been proposed involving conditions, such as that justification for the belief must be infallible and that a true belief counts as knowledge only if it is produced by a reliable belief-forming process. Two types of conditions have been proposed:
Externalism: Externalists think that factors deemed "external," or outside of the psychological states of those who gain knowledge, can be conditions of knowledge.
Internalism: Internalists claim that all knowledge - yielding conditions are within the psychological state of those who gain knowledge.
Knowledge may be acquired in two ways:
1. A priori knowledge is known independently of experience.
2. A posteriori knowledge is known by experience, i.e. it is empirical, or arrived at afterwards.
Certain views treat all knowledge as empirical and based on perceptual observation by the five senses, while others regard disciplines such as mathematics, economics, and logic as exceptions. Rationalists believe that knowledge is primarily (at least in some areas) acquired by an a priori process or is innate.
Constructivism considers all knowledge to be "constructed," in as much as it is contingent on convention, human perception, and social experience.
Perception is the ability to take in information via the senses and process it in some way. Vision and hearing are two dominant senses that allow us to perceive the environment. The study of hepatic (tactile), olfactory, and gustatory stimuli also falls into the domain of perception. Much of our perception is representational: we take the world to be a certain way, sometimes correctly and sometimes incorrectly.
It also seems that there is a form of perception that does not require the possession of concepts (although this claim has been questioned). It is plausible to claim that cognitively unsophisticated creatures, i.e. those that are not seen as emerging in conceptually structured thought, can perceive the world, and that at times we can perceptually engage with the world in a non-conceptual way. Perception that does not involve conceptual structuring is called "simple seeing." This perception involves the acquisition of information about the world that enables us to virtually discriminate objects and to successfully engage with them, but also of information that does not amount to one having a conceptually-structured representation of the world. These are all forms of perceptual experience, of causally engaging with the world using our sensory apparatus, and that have a distinctive conscious or "phenomenological" dimension. Seeing, in its various forms, strikes our consciousness in a certain way.
"The term "sensation" is used to refer to the conscious aspect of perception but note that one can have sensations even when one cannot not be said to perceive the world. When hallucinating or dreaming, for example, one has sensations that usually characterize perceptual experience, even though one's experience cannot be described as perceptual, per se.
Consider how these various kinds of perceptual experiences are related to our perceptual beliefs. Perceptual beliefs are those concerning the perceptible features of our environment and are grounded in our perceptual experience of the world. Just how our perceptual beliefs are grounded in our perceptual experience is a contentious issue. There is certainly a causal relation between the two, but some philosophers also claim that it is perceptual experience that provides justification for our perceptual beliefs."
"Objects of perception are the entities we attend to when we perceive the world. Perception lies at the root of all our empirical knowledge. We may have acquired much of what we know about the world through testimony, but originally such knowledge relies on the world having been perceived by others or ourselves using our five senses: sight, hearing, touch, taste, and smell. Perception, then, is of great epistemological importance. In the following sections, I briefly review the theories of perception."
Perceptual realism is the common-sense view that objects exist independently of perceivers. Direct realists also claim that we directly engage with these objects: it is these objects themselves that we see, smell, touch, taste and listen to. "There are, however, two versions of direct realism: naïve direct realism and scientific direct realism. They differ in the properties they claim the objects of perception possess when they are not being perceived. Naïve realism claims that such objects continue to have all the properties that we usually perceive them to have. Scientific realism, however, claims that some of the properties an object is perceived to have are dependent on the perceiver, and that unperceived objects should not be assumed to retain them."
"Scientific direct realism is often discussed in terms of Locke's distinction between primary and secondary qualities. The Primary qualities of an object are those whose existence is independent of the existence of a perceiver. The secondary qualities of objects, however, are those properties that do depend on the existence of a perceiver. In the former interpretation, a cup itself is not yellow, but the physical composition of its surface, and the particular way this surface reflects light rays into our eyes, causes in us the experience of seeing yellow. In the latter interpretation, for an object to be yellow is for it to be disposed to produce experiences of yellow in perceivers. "The secondary qualities, then, comprise such properties as color, smell and texture.
"The indirect realist agrees that the cup exists independently. However, through perception I do not directly engage with this cup; there is a perceptual intermediary that comes between us." "This intermediary has been given various names like "sense datum," and the plural, "sense data." Sense data are mental objects that possess the properties that we take the objects in the world to have. They are usually considered to have two rather than three dimensions. I perceive the coffee cup by virtue of the awareness I have of the sense data that it has caused in my mind."
We also look at the stars in the night sky. It is a fact that the star at which we are currently looking may have ceased to exist. How can we, then, be directly attending to that star when it is no longer there? This argument can be applied to everything we perceive. One should, therefore, accept that all the events we perceive are to some extent in the past.
There are many neurophysiological features and physiological entities such as retinal images that are involved in perception. They are, however, intermediaries in a different sense. They are simply part of the causal mechanism that enables us to perceptually engage with objects. So we do not have any reason to give up direct realism.
Illusions occur when the world is not how we perceive it to be. When a stick is partially submerged in water, it looks bent when in fact it is straight. We can also have hallucinations in which there is nothing actually there to perceive at all. If the bent shape is not a physical object, it must be something mental, the "sense data." According to Locke, "the mind perceives nothing but its own ideas" (ideas are mental components akin to sense data).
Sense data are seen as inner objects and are incompatible with a materialist view of the mind. Indirect realism is committed to dualism. The first and greatest problem for the dualist concerns explaining the interaction between mind (soul?) and body. "A non-physical sense datum causes physical movement. Such causal relations seem to be counter to the laws of physics. The physical view of nature aims to be complete and closed: for every physical event there is a physical cause. The only way to maintain both physical closure and the causal efficacy of the mental is to claim that there is over determination, i.e. that the physical action has two causes, one involving sense data, and one involving purely physical phenomena, either of which is in itself sufficient to bring about that action. "
A second problem associated with the non-physical nature of sense data concerns their spatial location. The relative positions of physical objects in physical space must more or less correspond to the relative positions of sense data in our private spaces. But the non-physical does not have spatial dimensions.
Another problem with indirect realism is adverbialism. Our perception should be described in terms of adverbial modifications of the various verbs characteristic of perception, rather than in terms of the objects to which our perceptual acts are directed. Indirect realism also invokes the veil of perception. All we actually perceive is the veil that covers the world, a veil that consists of our sense data. What, then, justifies our belief that there is a world beyond that veil?
3. Phenomenalism
Phenomenalists hold that propositions about the physical world should be seen as propositions about our possible experiences. Physical objects can exist unperceived since there is the continued possibility of experience. For Phenomenalists, there is no world independent of our (possible) experiences.
For many, the idealistic nature of phenomenalism is unpalatable. A consequence of phenomenalism would seem to be that if there were no minds then there would be no world. A key argument against phenomenalism is the argument from perceptual relativity. There are no laws like conditional statements that describe the relation between sensations considered in isolation from physical aspects of the perceiver and of the world.
4. The Intentional Theory of Perception
"Intentionalists emphasize parallels between perceptions and beliefs. Beliefs possess "about"- ness or what philosophers of mind call "intentionality." Intentionality is considered to be an essential feature of the mind (soul), and it describes the property that certain mental states have of representing being about certain aspects of the world. The aspects of the world that a belief is about can be specified in terms of its intentional content. The intentionalist claim is that perceptions are also representational states."
There are problems associated with accounting for the phenomenological features of perception. Our experience consists in more than simply representing that the world is a certain way; it is also the case that the way we acquire representations strikes our consciousness distinctively. There is, however, something "it is like" to be having such representations. Our experience has a phenomenological dimension, a dimension that you are probably currently imagining. The intentionalist, therefore, must also account for these phenomenological properties of perception.
One route that the intentionalist could take is to identify the phenomenological aspects of our experience with the representational. The second broad response to the phenomenology of experience is to claim that representational properties alone cannot account for perception, and thus one should reject the intentionalist project. If one is to account for what it is like to perceive the world, then one also requires sensational properties (properties distinct from those relevant to representation). Concepts of sensation are indispensable to the description of the nature of any experience. Some philosophers favor the existence of qualia (singular: quale). These are seen (by some) as the non-representational, phenomenological properties of experience. Others take qualia to be essentially private, and our knowledge of them to be incorrigible.
5. Disjunctive Accounts of Perception
"Disjunctivism denies the key assumption that there must be something in common between veridical and non-veridical cases of perception, an assumption that is accepted by all the positions above, and an assumption that drives the argument from illusion. For the disjunctivist, these cases certainly seem to be the same, but they are, however, distinct. This is because in veridical perception the world is presented to us. The world is not just represented as being a certain way, as for the intentionalist; but rather, the world partly constitutes one's perceptual state. Thus, one's perceptual state when hallucinating is entirely distinct from one's perceptual state when actually attending to the world."
"Disjunctivism can avoid the argument from illusion since it does not accept that veridical and non-veridical perceptual states are in any way the same (they only seem to be). Intentionalists answer the argument from illusion by claiming that veridical and non-veridical perceptions have a type of representational state in common, whereas disjunctivists undercut the argument by claiming that there is no need to posit such a common factor."
"However, in any particular case the disjunctivist must accept that he cannot tell which disjunct holds. When prey to illusion or hallucination, it can seem to you as if you are really perceiving the actual state of the world, and thus, it seems to you that you are in the same perceptual state that you would be in if the world was really how you perceive it to be. A consequence of disjunctivism, then, is that one can be not only deluded about the state of the world, but also about the state of one's own mind. "
A consequence of disjunctivism is that two physically identical brains can be in distinct perceptual states. "The contents of the brain alone do not determine the nature of our thoughts and experiences. There is, however, some notion of supervenience maintained in that the mind supervenes on the brain together with its causal links to the environment: if there are two identical brains causally connected to the same features of their environment, then the mental states manifest in those brains must also be identical. Various arguments have been forwarded for this externalist position. Thought content is not in the head. Disjunctivists hold a parallel claim: since it is the state of the world that determines the content of one's perceptual state, hallucinations have nothing perceptually in common with veridical perceptions even though all could be the same inside one's head. "
