David Hume's Empiricism: Knowledge, Impressions, and Causality

Hume's Philosophy of Knowledge

This text summarizes and simplifies the themes of Book 1 of David Hume's Treatise of Human Nature, a work largely misunderstood in his time. The original investigation is divided into 12 sections.

In his profound investigation of human knowledge, Hume presents his interpretation of how we acquire and process information. This perceptual empiricism identifies the fundamental components of knowledge, distinguishing between two primary types:

• Impressions: Vivid and forceful perceptions, such as sensations, passions, and emotions.
• Ideas: Faint images of impressions in thinking and reasoning. Ideas are less intense copies of original impressions.

Types of Impressions

Hume further categorizes impressions into two kinds:

• Impressions of Sensation: These arise in the mind from unknown causes, such as sensory experiences (e.g., seeing, hearing, feeling).
• Impressions of Reflection: These are derived from ideas, such as emotions or passions that arise from our ideas of pleasure or pain.

Simple and Complex Ideas

Ideas are considered simple when they correspond to a single, indivisible impression. Conversely, they are complex if they are formed from multiple simple ideas, either by:

• Memory: Faithfully reproducing original impressions.
• Imagination: Altering or combining simple ideas in new ways.

Principles of Association of Ideas

Hume identifies three fundamental principles by which ideas are associated in the mind:

1. Resemblance: Ideas that are similar tend to be connected.
2. Contiguity: Ideas of objects that are close in time or space tend to be connected.
3. Causation: Ideas of cause and effect are strongly linked.

The Problem of Causality

The causal connection is subjected to a detailed analysis by Hume because he considers it a crucial, yet problematic, concept in human understanding.

Reasoning About Matters of Fact

Hume argues that only relations of ideas (e.g., mathematics, logic) can be reached through pure understanding and express necessary relations. In contrast, matters of fact, which are derived from experience, are empirical and not necessarily true. Our reasonings about matters of fact seem to be based on cause and effect. However, Hume contends that this relationship is not demonstrated in a way that, given some premises, the conclusion follows necessarily.

The Nature of Causal Connection

When observing any object or event, we are unable to discover what will follow it solely through reason. We rely on experience, yet we often believe there is a necessary connection between cause and effect. The concept of a necessary causal connection has deep philosophical roots, often attributed to thinkers like Plato and Parmenides. To deny this necessary connection, Hume argues, would indeed challenge traditional metaphysics.

However, for Hume, every idea must ultimately derive from an impression. Where no corresponding impression exists, we are dealing with a fiction of the mind. In the causal link, we cannot find an impression that corresponds to a necessary connection between cause and effect. This link is a product of the imagination, connecting two objects or events that are habitually observed to occur one after the other.

Belief and Experience in Causality

Only in our imagination, as a result of the habit of seeing events appear together, do we believe in a necessary connection. In reality, all such relations are contingent. However, Hume acknowledges that causal associations, though not logically necessary, are supported by experience. This makes them not incorrect, but rather very reasonable arguments that guide us in future expectations. This belief is reliable, more so than any other that lacks such empirical support.

For example, there is no necessary connection between fire and smoke. Yet, our experience of their frequent association allows us to infer the existence of fire if we see smoke. Similarly, from the intricate skill evident in a watch, we might infer the existence of a watchmaker, or from the complexity of the world, a creator.