This permits thought to pass from an actual impression to the idea of other impressions obtained in the past, and from these ideas to other ideas. This is the law of association of ideas , a fundamental point in Hume's doctrine and the basis for complex ideas . Thus ideas are naturally associated with one another and form large groups, and these groups in turn are related, to form still larger groups. The belief that behind these groups of representations there is a reality corresponding to them gives origin to belief in an external world , regulated by the same laws that exist in the world of thought. Another fundamental law of Hume's theory of knowledge is that of habit .
Impressions succeed one another with a certain constancy .
For example, every time I have drawn near the stove, I have felt warm. Hume answers in the negative. Outside these two types, there is no certitude, philosophical or scientific, strong enough to excluded all doubt. All Rights Reserved.