ations but impressions are the cause of the sensation. An impression is part of a temporary feeling, but an idea is the permanent impact of this feeling. Hume believed that ideas were just dull imitations of impressions. Hume did not believe that a priori, knowledge based on reasoning can deduce true knowledge. Knowledge based on reasoning alone, according to Hume does not provide understanding of the real world. He believed that all ideas have to have impressions, that the human mind invented nothing. So, according to Hume, a priori reasoning does not offer any understanding of the real world, because they cannot be traced to the impressions that first created them. The human mind takes simple ideas, and turns them into complex ideas. (243) An example of this concept is the idea of an unicorn. Unicorns are conceived as being horses with horns. Humes claimed that an unicorn is formed of two simple ideas, the figure of a horse and a horn. Hume concludes that our beliefs can never be rationally justified, but must be acknowledged to rest only upon our acquired habits. In similar fashion, Hume argued that we cannot justify our natural beliefs in the reality of the self or the existence of an external world. From all of this, he concluded that a severe skepticism is the only defensible view of the world, though he does not expect us to live our daily lives by this notion. Wesley C. Salmon points out that according to the principle of uniformity of nature that even though we do not know for sure what will happen in the future, we must assume that nature will continue as it has done in the past. This is the human condition, in that we have no way of asserting what will happen in the future. But in living our daily lives, we are better to go by what has occurred in the past in nature, despite Humes philosophy that there is only a 50/50 chance. In order to function, we ...
