The remembrance of perception is merely a copy of actual perception, and all ideas are merely weaker copies of Impressions. Hume explains that it will seem that thought is unbounded and limitless, but actually thought is confined within very narrow limits. The apparent boundless creativity of the mind comes from compounding, transposing, augmenting, or diminishing the materials afforded us by the senses and experience (2, 13 par. 1-2). By this Hume means that no matter how far-fetched the products of imagination becomes, all ideas are connected and ultimately traceable to an Impression or Impressions.
(3, 18). According to Hume, the mind normally connects ideas with each other through one or more of three basic principles: Resemblance, Contiguity, and Cause-and-Effect (3, 19), and that all reasonings concerning matter of fact seem to be founded on the relation of Cause and Effect. (4. 1, 22). However, Hume claims knowledge of cause and effect, without exception, is never attained by a priori reasoning. All knowledge of cause and effect comes entirely from experience. (4. 1, 23 par. 2). Every effect is a distinct event from its cause. It could not, therefore, be discovered in the cause.
(4. 1, 25, par. 2). All reasoning can be categorized into two: demonstrative reasoning (concerning relations of ideas) and (intuitive) moral reasoning (concerning matter of fact and existence). Hume points out that all thought concerning existence are based on cause-and-effect, which in turn is based entirely on experience. Any conclusions that we derive from experience are based on the assumption that events of the future will conform to events of the past. (4. 2, 30 par. 2). However, this is not intuitive nor demonstrative (4. 2, 32).
For instance, there is no process of argument through which, for instance, a person can conclude that whenever a billiard ball is hit by another billiard ball, it will move. (4. 2, 33 par 2). Even a highly intelligent person who for the first time observes the world would witness a sequence of events but would not be able to determine any cause and effect relationships between what he witnesses. Such a person, without more experience, could never employ his conjecture or reasoning concerning any matter of fact, or be assured of anything beyond what was immediately present to his memory and senses.
But eventually, through experience, he will be able to form conclusions about the cause-and-effect relationships of events and objects. (5. 1, 35 par 1). According to Hume, the principle through which a person can form these conclusions is Custom or Habit (5. 1, 36). Humes concluding words are that any piece of literature that does not have abstract reasoning concerning quantity or number nor experimental reasoning concerning matter of fact and existence ¦can contain nothing but sophistry and illusion.
The nature of knowledge according to Immanuel Kant For Immanuel Kant, knowledge (and thus reality) is constructed by the mind, not passively derived through the senses. In other words, the mind shapes the world. Kants Critique of Pure Reason is an attempt to answer the problems of the nature of knowledge”what it is and how it is obtained. Kant looks at the relationship between a priori knowledge, or knowledge based on reason alone, and a posteriori knowledge, or knowledge gained from the world.
According to Kant, we have a priori intuitions and concepts. We have innate, logical knowledge, and this knowledge enables us to grasp a posteriori knowledge, to understand the external world. For example, Kants view is that space and time are just mental constructs, that space and time are forms of seeing, which serves as a precept to our experiences (Kant, a20-a23, a25-a38). Another example is the notion of causality, which in Kants view is a form of organizing mechanism that we impose upon nature to render it understandable (2a1-2a19).
Kant argued that reality, as we perceive it, cannot be accounted for purely by sense perception. Kant holds that what we refer to and perceive as the external world is an artifice of the mind. His argument is that the mind itself contributes substantially to, and even synthesizes, its own knowledge (i11). According to Kant, the appearances of things are objects of intuition, which is one form of (mental) representation. For him this includes physical sensations (such as pain). Kants view is that appearances do not exist by themselves, but only relatively to external reality.
That is, appearances do not exist independently of the human power of representation (t21). According to this view, the world, as we perceive it, is not actual reality, but is a phenomenon of actual reality as constructed by the mind. He argues that the shape of an object, for example, does not come from the object itself, but comes from us, as a result of interaction with the object Sensory input needs to be processed and recognized through the filter of the mind or it would not mean anything to us.
For Kant, there are things-in-themselves, which exist independently of the human mind, and appearances, which exist only in the mind. The existence of appearances, according to Kant, entails the existence of things-in-themselves, but not in the way that we know. Thus, since the existence of things-in-themselves is just a hypothesis, the relationship of our perceptions to actual reality remains suspect, and we can never really be sure if what we perceive are not just purely constructs of the mind (p38).
Hence, for him, we can never really know the true reality, because this reality is only perceived as it is filtered through our senses, senses that structure reality. We can only gain knowledge of appearances. Criticism of Hume There are some important difficulties in Humes work that he fails to address. One flaw in Humes arguments that Kant points out is that one of Humes fundamental assumptions is that perceptions (or Impressions) correspond exactly to the real world, although for many other philosophers the very nature of reality was a problem.
Another is that Hume assumes that all knowledge comes from experience, but the notion of causation and necessity are also not explained by Hume, who claims that everything that one knows is ultimately traceable to the senses. It can be argued that the perception of causation and necessity come from a priori knowledge.
References Hume, David. An Enquiry Concerning Human Understanding. 23 Dec 2006.