Understanding Hume’s Theory of Knowledge
**Relation of Ideas**
Hume points out two types of knowledge: knowledge relationships between ideas and propositions based on experiences. As regards the relations of knowledge of ideas, he says that although all ideas are based on impressions, we have knowledge of ideas without the need for impressions. These formulations are typical of analytics and necessary knowledge. It is the knowledge of logic and mathematics. What we know of ideas is reduced to relationships between ideas based on three principles: similarity, contiguity, and causality. Ideas are reduced to impressions, and the mind mixes, implements, increases, or decreases said impressions.
**Impressions**
Impressions are the knowledge of the senses. For Hume, the origin of knowledge is in experience; he understands knowledge as impressions. Therefore, knowledge is limited. Hume divides all perceptions of the mind into two classes according to the degree of force or vivacity. Impressions are more intense than ideas and thoughts. That is, the distinction between ideas and impressions is that ideas are the less lively perceptions of which we are conscious because they are copies of our more intense perceptions.
**Ideas**
To study the nature of ideas, Hume relies on the origin of knowledge in experience. Feeling is the basis of empiricism. Thus, he introduces a criterion to decide on the truth of our ideas: an idea is true if it proceeds from some impression; otherwise, it is false. Therefore, the limit of knowledge is impressions. Both our ideas and impressions can be simple or complex.
**Ideas of Cause**
The idea of cause is a problematic concept for Hume. According to the author, our knowledge is reduced to current and past impressions, but we cannot have knowledge of future events because we do not have impressions of something that has not yet happened. But in reality, we talk about future events and affirm their cause. Hume criticized this relationship: we do not know the cause through the senses, considering the strong wind as an effect. Hume derives the following relations from causality:
- The first is that of nearby objects and events.
- The second is “temporal succession.” We affirm that events follow one after another because the first is the cause of the second.
- The third is that which could explain causation, the “necessary connection,” but it cannot be proven through experience.
**Phenomenology**
Phenomenology is a philosophical theory according to which no knowledge is possible of something different from our own perceptions. Hume believed that this philosophical position is the only reasonable one but contrary to the natural beliefs of common sense. Classical empiricism defended a thesis that, if carried to the end, inevitably leads to phenomenology: when we perceive, what we really perceive is not external to our mind but our own sensations. They reached this point of view in different ways, but essentially by noting that in the act of perception, the object perceived is not a real part of the very experience of perception, it is not included as an object in perception itself but presents as something external to our minds, and is the object perceived or inferred. The viewpoint of phenomenology is so strange and contrary to common sense ideas that no empiricist accepted it fully and consciously.
**Metaphysics**
Hume understands true philosophy (as opposed to the classical metaphysical sense as a system encompassing the world) as setting limits to the capacities of human knowledge.