Immanuel Kant's explanation on how we gain knowledge is preferable to that of David Hume. The mind can be compared with the computer in illustrating how the mind gathers and processes information or sense-data from generalizations, which in turn derive from a categorical imperative. A person need not experience something before he can apprehend or learn it.
Exposition. David Hume believes that all ideas are derived and become knowable only from sense experience (Lavine 1985, Stevenson 1987, Wikipedia 2006, Morris 2001).. From this standpoint, he rejects that we can know that every event has a cause, as he rejects the necessary connection between cause and effect, i.e., that the effect can proceed only from its cause. Just because something occurs after another on a regular and even observable basis does not mean that the former is the effect of the latter. To him, the effect may just happen without the connection to a cause. Not only is there more than one cause to an effect or more than one effect from a single cause, but also that certain causes to an effect - and the effects of certain causes - are still unknown in the world. The cause for cancer is one of these unknowns, although we are certain that there is a cause. He also argues that the idea of substance is without meaning and incoherent, since that substance cannot be subjected to the test of physical experience. Hume, moreover, maintains that every object has observable properties, which are completely distinct: whereby the property that is seen - visual sense-datum - and the property that is felt or touch - tactile sense-datum - both belong to the same object. That object may appear one way and feel another way - their properties are incompatible - and their sense-data provide that connection that they both belong to that specific enduring object. They are incompatible because the different senses perceive different sense data and perceive them differently. If the properties of all objects were compatible or pure and if no enduring objects existed, the world would be chaotic. Things would look, feel, smell, and taste the same. We would not need to differentiate one thing from another. We would not know what to expect next. We take recourse in common sense that such incompatible properties of such enduring objects do exist. Science, therefore, has to exist and presuppose that all effects have causes and vice-versa (Lavine, Stevenson, Wikipedia, Morris).
Hume holds that human ideas are nothing but copies of impressions and that it is impossible to think of what one has not already felt beforehand, either through one's external or internal senses (Lavine 1985, Stevenson 1987, Wikipedia 2006, Morris 2001).
His skepticism consists chiefly in the denial of the certainty of a thing, such as God, a soul or a self, unless the impression from which the idea is derived is clearly established or pointed out. He dismisses moral philosophical systems and hypotheses as having perverted natural understanding. He views these theories of "monkish virtues" offered by selfish schools as mere accounts of human nature, which experience and observation prove false. He rejects moral judgments as deriving from reason and holds that t is difficult even to make their hypothesis intelligible. He argues against reason as judging matters of either fact or of relations. He does not view morality as consisting of a single matter of fact, which can be immediately perceived, intuited or grasped by reason alone. All knowledge can come only through the senses, whether as ideas or impressions. Impressions are lively perceptions of the senses, feelings, love or hate. Ideas, on the other hand, are less lively perceptions, derived from reflections of those livelier perceptions. He also rejects causation, whereby a cause produces an effect or an effect resulting from a particular cause. Instead, he links causation to mere superstition and explains away the instinctive tendency to accept causation as accounted for by the development of habits in our nervous system, which cannot be eliminated but which cannot prove true, by any deductive or inductive argument, this belief in the reality of the external world (Lavine, Stevenson, Wikipedia, Morris).
Immanuel Kant, on the other hand, maintains that the concept of a substance need not be experienced directly in order to be meaningful and coherent. It is sufficient that the concept functions in such a way as providing the connection between its empirical properties (through the senses) and indirectly leading to our sense-data of these properties. This approach is of prime importance to our living in this world in an orderly manner. We cannot co-exist with random sense-data. And since that cannot be derived from direct sense experience, it must come from the mind, which functions to connect our sense experiences to something. In other words, the mind processes and synthesizes experience (Abbot, trans, 2006; Richards 2006; McCormick 2006). Kant states that there must be something in every person that separates and relates his experiences - the "self." This is his response to Hume's argument that that something must do the relating and the recalling of past experiences, but that this something cannot be one of those related and recalled. That something must also possess an awareness of these experiences to be related and recalled. He, however, disagrees with Hume that the self is only a bundle of separate experiences and thoughts at random. It must be something that recalls those past experiences and synthesizes all experiences of the world outside (Abbot, Richards, McCormick).
This "self," though, in agreement with Hume, is unobservable because only experiences and thoughts can be the objects of introspection (Abbot, trans, 2006; Richards 2006; McCormick 2006). But it is observable and knowable precisely through its function or action of synthesizing of experiences. At this point, Kant and Hume agree that the "self" must be presupposed. This self is what Kant calls the Transcendental Ego
Kant used the computer as an analogy of the mind or self. A computer output is determined by the input and the program of the computer. Kant compares sensory experiences with a computer input and the mental rules followed in arranging the experiences with the computer program. Like the countless computer processes, those of the mind are complex and go through several stages, levels and kinds of processing, most of them unconscious, speedy and efficient. Just like the computer output, the mind's product of synthesis of experiences is the result. Because the mind produces such a synthesis - our everyday world - according to a very general or universal rules of operation he calls "categories," these rules or categories will always be ingrained in the empirical or synthesized world of our experience. The mind supplies the appropriate concepts in organizing and unifying sense-data, and it requires the a priori concept or category of substance in doing this. It is also what the mind needs and uses in recognizing and arranging sense impressions into causes and effects. If this were not done, we would not experience anything but only random sense impressions in a meaningless world. Furthermore, the self shares the mind's job of synthesizing sensory experiences. In so doing, the self recognizes the dimensions of time and space. The mind that does this job is not just a spectator but also a participant who must react to the environment wherein it performs this function. The self must know where it is posited in order to interact effectively with and in the environment, or the world, which its synthesized experiences create. The term "world" is here used in two different ways to mean two different things. The first is the physical location where everything exists, including the physical laws that maintain its existence. The second is in the person himself or herself, as when we say that people live in different worlds or their beliefs are worlds apart. That person must find his or her place in his or her own world. His or her "self" created his or her world and that self does the synthesizing of his or her experiences. This "self," which is part of the world, is what Kant calls the Empirical Ego as distinguished from the Transcendental Ego. In presenting the one criterion for moral obligation, he first rejects other moral traditions before his time: among them, the virtue theory, which bases morality on good character traits; and the consequential theory, which bases it on the consequences of actions. In response, he argues that moral actions are based only on a "supreme principle of morality" - one that is objective, rational and freely chosen -- which he called the categorical imperative (Richards, Abbott, McCormick).
In his principal book entitled, "The Foundations of the Metaphysics of Morals," Kant explains why only the categorical imperative is the valid standard of moral obligation (Abbott 2006, Richards 2006, McCormick 2006). He limits his discussion to specific willful actions in moral situations or conditions, where the will is, or should be, influenced only by reason or rational considerations, rather than…