Hume’s Empirical Science of Man: Cause, Effect, and Custom
Hume’s Empirical Science of Man
Introduction
David Hume aimed to establish a science of man grounded in experience and observation, rejecting speculative philosophy. This involves analyzing human understanding, its capabilities, and limitations. He distinguishes between two objects of human reason:
- Relations of Ideas
- Matters of Fact
Relations of Ideas vs. Matters of Fact
Relations of ideas belong to mathematics and demonstrate certainties. These are purely rational, requiring no experience. Contradicting a demonstrated proposition is impossible. Matters of fact, however, concern empirical sciences like history. Denying a matter of fact doesn’t imply a contradiction; both a proposition and its opposite can be conceived. Matters of fact rely on empirical evidence and probability, based on past experience. This is Hume’s focus.
Causality and Inference
Hume examines causality through the example of colliding billiard balls. We observe:
- Contiguity in space and time
- Priority of the cause
- Constant conjunction: similar causes produce similar effects
The question is, what justifies inferring a causal connection? Hume argues this isn’t based on reason. Even Adam, with innate knowledge but no experience, couldn’t predict effects from observing objects. Causal connections aren’t demonstrable because we can conceive of opposite effects without contradiction. The rationale is the repeated experience of constant conjunction. However, experience only informs us about the past. Extending this to the future assumes nature’s uniformity.
The Problem of Induction
The assumption of uniformity isn’t based on demonstration (it doesn’t imply a contradiction for nature to vary) nor probable arguments (which themselves rely on uniformity). Hume argues it arises from custom or habit. We’re conditioned to assume the future resembles the past. This isn’t a belief in the sense of a new idea, but a feeling of assent. Belief distinguishes conceptions we assent to from those we merely entertain.
The Role of Belief
When we believe in a necessary connection between cause and effect, we’ve acquired a mental connection. Aligning our thoughts with external reality is not rationally justified but psychologically grounded. This principle in the mind operates regularly and underlies our understanding of matters of fact. Hume’s radical empiricism critiques inductive inference. Inferring from a particular case requires generalization based on repeated experience. But accumulated experiences don’t automatically guarantee universality. Extrapolating to the future relies on the metaphysical assumption of nature’s uniformity. Causal relations appear necessary due to custom, extending the observed constant conjunction to the future based on the assumed conformity of the future with the past.