David Hume argued that man gains knowledge through experience and that we should be skeptical of all other. Hume set up criteria for determining cause and effect. These criteria explained his skepticism about causality and why he came to the conclusion that humans were not capable of discovering truth. In order to fully understand Hume?s analysis of causality, we must first understand the importance he placed on the senses. Hume is skeptical of all that is not in some way connected to our senses. Hume separated human perceptions into two different categories: impressions and ideas. Impressions include sensations and emotions. They are original and more dynamic and lively than ideas. They are what we see, hear, feel, love or hate. For example, if I place my hand on a hot pan and feel the heat, I have an impression. Later, when I go over the experience in my thoughts, I may recall heat.
I remember heat equals pain. Hume thought that because of this, there are no innate ideas, and that all ideas must come from experience, and therefore relies on our senses. The only connection that is noticeable is a mental one, which takes place within the human mind. He referred to this pattern as the associations of ideas. Hume argues that in order for the third criteria to be determined we must be able to predict the future, which of course is not possible. No matter how consistent our experiences, we can never determine the consistency of tomorrow. The impression of the color blue, for example, is simple. The principle that all simple ideas derive from simple impressions plays an important role in Hume?s analysis of causality. Hume insisted that there is nothing we can discover from our experiences that tells us that nature will remain constant,