David Hume's Philosophy: Causality, Skepticism, and Empirical Limits

Hume's Challenge to Causality

If we accept only what experience offers, we find that causality is not an inherent property we observe directly. Experience presents us only with a succession of phenomena.

We cannot observe either the power in A to produce B, or the direct link between A and B where A is the cause of B. The forces through which bodies supposedly operate are entirely unknown to us. The connection between cause and effect, therefore, appears arbitrary.

The only things we consistently find are specific patterns in the succession of phenomena:

• Spatiotemporal Contiguity: Cause and effect are close in space and time.
• Priority in Time: The cause always precedes the effect.
• Constant Conjunction: The same causes are always followed by the same effects.

Hume argues that everything we experience, while appearing perfectly ordered, could be otherwise. Our natural inclination to speak of necessity, however, leads us to believe that specific effects must follow specific causes.

The Contingency of Causal Principles

The principle that "everything that begins to exist must have a cause of its existence" neither possesses inherent certainty nor can it be demonstrably proven.

Hume asserts that our belief in this principle stems from custom and habit. Because we have consistently observed successions between phenomena, our minds are led by experience to assume that nothing can begin to exist without a preceding cause.

Limiting Causality to the Empirical World

Hume argues that, given the restrictions implied by his earlier criticism, if we continue to believe in causality, we must limit its application strictly to the empirical world.

We cannot, however, extrapolate from the observed empirical world to metaphysical realities such as God and the soul, for which there is no empirical experience whatsoever.

Hume's Skepticism and the Rejection of Metaphysics

Cartesian certainties are once again opened to doubt. In our minds, there are only impressions and ideas derived from them. Nothing, however, allows us to establish a direct relationship between our perceptions and the external objects they supposedly represent.

Mathematical reasoning alone can achieve certainty, but its scope is limited. Humans live in a world of facts and need to understand them.

Hume was aware that philosophical skepticism (the view that our knowledge of reality can only attain a degree of belief), while a result of philosophical inquiry, cannot be sustained in our daily lives. Our practical lives depend on assuming some knowledge of reality.

This skepticism serves to highlight the limits of our knowledge. It is a rejection of any metaphysical dogma, aiming to confine our capacity for knowledge within the framework provided by experience.

With his theory of knowledge, Hume dissolves the concepts of substance and causality, arguing they are merely relations of ideas that cannot be explained by experience. He thus removes metaphysics from the common ground on which it traditionally stood, reinforcing his skeptical stance.

Hume argues that human knowledge is limited to simple phenomena, denying the existence of any reality that bears no relation to these phenomena.