David Hume’s Empiricism: Knowledge, Self, and Causation
Hume’s Philosophy Contrasted with Plato
Hume’s philosophy stands in opposition to Plato’s. Hume, an empiricist, believed that knowledge originates solely from sensory experience, aiming to combat abstract beliefs or superstitions, such as the concept of God. Therefore, according to Hume, we cannot gain knowledge beyond sensory experience. This contrasts sharply with Plato, who posited an ideal, perfect world (the World of Forms or Ideas) accessible through reason, where true knowledge resides.
Furthermore, Hume argued against innate ideas, proposing that the mind is a ‘tabula rasa’ (blank slate) at birth. Knowledge is acquired gradually through experience. Conversely, Plato believed in innate knowledge through his doctrine of Reminiscence (Anamnesis). He suggested that the soul, having existed in the World of Forms before entering the sensible world, forgets its prior knowledge upon incarnation, and learning is essentially a process of remembering.
Perceptions of the Mind
Hume categorized perceptions into two types:
- Impressions: Vivid and forceful perceptions, arising directly from sensory experience (external) or introspection (internal).
- Ideas: Less vivid copies or reflections of impressions, used in thinking and reasoning. These can be simple (derived from simple impressions) or complex (combinations of simple ideas).
According to Hume, all valid ideas must ultimately be traceable back to the original impressions or experiences from which they derive.
Laws of Association
Hume proposed three principles by which ideas connect in the mind:
- Similarity: The mind associates ideas that resemble one another (e.g., a picture reminds us of the person).
- Contiguity in Time or Place: Ideas of things experienced close together in time or space tend to be associated (e.g., thinking of one room in a house leads to thinking of adjacent rooms).
- Cause and Effect: Observing an event consistently followed by another leads the mind to associate them as cause and effect (e.g., seeing fire and feeling heat).
Relations of Ideas vs. Matters of Fact
Relations of Ideas
These are truths known a priori (independent of experience), based purely on the logical relationships between ideas. They are necessarily true, and their negation implies a contradiction. Example: “All bachelors are unmarried.”
Matters of Fact
These are truths known a posteriori (based on experience). They deal with the actual state of the world and are established through observation. Their negation is conceivable without contradiction. Example: “Clouds bring rain” (this is confirmed or denied by observation and experience).
Hume’s Skeptical Criticisms
1. Critique of the Self (Thinking Substance)
Hume argued that we have no impression of a continuous, unchanging “self” or personal identity separate from the stream of our perceptions. We cannot empirically observe a distinct entity called “I” beyond the bundle of constantly changing sensations, thoughts, and feelings. This contrasts with Plato’s dualism, which separated the immortal soul from the physical body.
For Hume, the concept of “self” is merely a convenient way to link our various perceptions and experiences across time, a product of the mind’s associative principles, not a distinct substance.
2. Critique of Substance (Including God)
Hume extended his critique to the concept of substance in general, including both material substance (the external world) and spiritual substance (like God). We never perceive an underlying substance, only its properties (e.g., we see the color and shape of an apple, not the ‘substance’ of the apple itself). Our belief in an external world stems from the consistency and coherence of our perceptions, leading us to infer the existence of objects independent of our minds. However, Hume argued we cannot empirically prove that these perceptions are caused by external objects or a divine being (God).
3. Critique of Causation
Hume famously analyzed the cause-effect relationship, questioning our basis for believing in necessary connections between events (e.g., that fire must cause heat).
He argued that our idea of necessary causation is problematic for two main reasons:
- The principle “Everything that begins to exist must have a cause of existence” is not intuitively or demonstrably certain. We can conceive of something beginning to exist without a cause.
- Experience only shows us constant conjunction (one event regularly follows another) and contiguity (events are close in space and time). It does not reveal any observable necessary connection that compels the effect to follow the cause. We observe event A followed by event B repeatedly, but we never observe the ‘power’ or ‘force’ that links them.
Our belief in cause and effect, Hume concluded, arises from custom or habit. After observing the constant conjunction of two events, our minds develop an expectation that the second will follow the first in the future. This expectation is a psychological feeling, not a logical certainty. The future might not resemble the past (this relates to the problem of induction, sometimes illustrated by the ‘turkey’ or ‘chicken’ example – the bird expects to be fed daily until the day it is slaughtered).
Understanding the Cause-Effect Relationship
Observed Elements (Experience)
When we observe what we call a cause-effect relationship (e.g., pressing an elevator button causes the door to open), our experience consists of:
- Contiguity: The cause and effect occur close together in space and time.
- Priority/Succession: The cause precedes the effect.
- Constant Conjunction (Repetition): We observe this sequence happening repeatedly.
Inferred Element (Mind)
Beyond observation, the mind infers a:
- Necessary Connection: A belief that the effect must follow the cause.
- Prediction: Based on past experience (constant conjunction) and the inferred necessary connection, we predict future occurrences (e.g., predicting rain tomorrow because it rained yesterday and today). Hume argues this inference is based on habit, not logic or direct observation of the connection itself.