Empiricism vs. Rationalism: Hume's Theory of Knowledge

Hume's Theory of Knowledge

Descartes, a representative of rationalism, held that both data and ideas lead to rational knowledge. There is no evidence that experience has value unless its contents are subjected to an ordered, rigorous and methodical procedure (methodical doubt and rules), so that we may arrive at clear and true ideas.

In the act of thinking, the mind acts according to its own content of thought, and not merely according to the first thing that depends on what it represents. Descartes admitted innate ideas, but only of three kinds: the self, God and the world. Through these, he explained the extrinsic attributes of bodies and their movements, which are the res cogitans and res extensa, whose modes or accidents act upon them.

Knowledge Originates in Experience

All knowledge, for Hume, comes from experience, which is the origin and limit of knowledge, and which has no independence of reason in itself. Take care of all the human mind: everything we perceive, whether thoughts or feelings, is composed of impressions, and all impressions originate from the senses.

The data of concepts are, in a very rich way, the first copy or derivation of the sensible impression that exists in our senses (not the innate idea itself, as Descartes said). Thought is a question of mental images whose constituents always come from our specific impressions; the mind has no direct contact with objects.

Two Types of Knowledge

Hume agrees that what knowledge can be before our senses falls into two types:

• a) Relations of ideas: These are deduced through demonstrative arguments, which are necessary and self-evident and always true. Their model is geometry, algebra or arithmetic. Example: "All bachelors are unmarried."
• b) Matters of fact: These relations are not deduced by necessary arguments, because the cause-effect relation is probable. Example: the collision of two billiard balls.

Impressions and Ideas

Hume makes the first division of perceptions into impressions and ideas, distinguishing between impressions of sensation (external experience = senses) and impressions of reflection (internal experience = passions, etc.).

Simple ideas derive from simple impressions, and complex ideas from complex impressions. Through association, imagination plays an important role on occasions, while complex ideas, such as cause-and-effect causality, have no true foundation in experience.

Induction and Reason

Hume considers it impossible to justify induction, since it is based on experience and not on thought. However, he employs the concept of reason in two senses: empirical and deductive. Empirical reason always refers to experience; whatever is reasonable has an empirical foundation, and a deduction grounded in experience is always permitted. On the contrary, rationalism relies on purely deductive, ideal continental reasoning that has forgotten its connection with experience and is rooted in meaningless philosophical problems.