Hume’s Empiricism: Analyzing Causality, Substance, and Self
Hume’s Theory of Knowledge: Ideas and Facts
Philosophical propositions can be categorized into two types:
Relations of Ideas
These propositions can be reached by reasoning alone, without recourse to experience. They are based on the rational principle of contradiction, making them universal and necessary propositions.
Matters of Fact
Matters of fact refer to propositions that rely entirely on experience. The only thing that guarantees the truth of propositions asserting facts is experience. These propositions are derived through experience, not reasoning, and their truth depends on empirical observation. This leads to particular and probable knowledge, not universal and necessary knowledge.
Every question of fact that yields new knowledge of the world requires experience to ascertain its truth. Moral standards, for instance, are matters of fact.
Hume’s Critique of Metaphysical Concepts
Hume critically examines several fundamental metaphysical concepts:
Critique of the Idea of Cause
Causality as a Necessary Connection
Hume scrutinizes the idea of cause as a necessary connection between two phenomena that are temporally and spatially contiguous. Causal inference involves deducing a consequent from an antecedent. For example, when you observe a phenomenon, you infer its origin. Seeing phenomenon X leads one to infer its cause Y. This assumes a necessary connection between the first and second phenomena. However, when two objects are independent, one cannot be considered the cause or effect of the other without a basis for reference.
When we say that one phenomenon causes another, what we are asserting is that they are necessarily connected; that is, it cannot happen that the former occurs without the latter following. Therefore, cause is defined as the necessary connection between two phenomena, temporally and spatially contiguous.
Experience vs. Reason in Causality
The relationship between cause and effect is not known a priori, meaning it cannot be discovered by pure reasoning. Only experience teaches us about cause and effect by showing certain facts in constant conjunction.
Consequently, we cannot have knowledge of future events because we cannot receive impressions of an event that has not yet occurred. Even when we observe an effect, the relationship with its alleged cause still does not appear to the mind as necessary, because cause and effect are independent of each other. That is, the effect is not contained within the cause, and the understanding could conceive numerous other effects.
The required causal connection is not a relation of ideas but, in every instance, a matter of fact. Therefore, the only way to establish its validity is through experience, specifically through an impression.
All we perceive are two phenomena, one we call cause and the other effect; the necessary connection itself is not perceived. The idea of cause is therefore not empirically valid.
Implications of Hume’s Causal Critique
The implications of this criticism are significant:
- All empirical sciences that base their conclusions on causal laws cannot provide universal and necessary knowledge.
- Aristotle’s concept of cause is invalidated.
The Role of Habit and Custom
What makes humans continue to expect the same effects from these causes is the principle of human nature called habit or custom. When we have repeatedly observed the constant conjunction of two phenomena, custom leads us to infer the existence of the one when the other is given, and without recourse to reasoning. This practice does not produce knowledge but only belief.
Critique of the Idea of Material Substance
Hume also challenges the concept of material substance:
Substance: A reality distinct from impressions, existing independently of them, and serving as the substrate through which impressions are given. However, the idea of substance does not stem from any impression.
Any impression we have is an act of our mind. We have impressions of smell, color, and shape, but not of material substance itself, only of the qualities that are supposed to emanate from it. Therefore, the idea of substance as an entity distinct from the material impressions of my mind is not empirically valid.
Critique of the Idea of Self or Personal Substance
A large majority of philosophers assert the existence of a spiritual substance, or ‘Self,’ distinct from our thoughts. For Hume, ‘Self’ or ‘personal substance’ refers to a substance distinct from our thoughts, which remains unchanged and constant throughout our lives.
However, there is no impression from which this idea arises. We only have our intuition of individual impressions, and the ‘Self’ is not an impression itself. Our impressions are not constant but variable. They never exist all at once but follow one another; therefore, there is no constant and permanent impression of the ‘Self’.
Hume thus denies the validity of the idea of a soul or enduring self. The only explanation Hume can offer is that our consciousness of personal identity arises from memory, through which we recognize the relationships between our successive impressions.