Rationalism vs. Empiricism: Hume on Knowledge and Morality

Posted on Mar 27, 2025 in Philosophy and ethics

Rationalism vs. Empiricism: Origins & Key Differences

Empiricism and Rationalism were prominent philosophical movements, particularly in the 17th and 18th centuries, with rationalism emerging slightly earlier.

• Rationalism: Developed mainly in continental Europe (e.g., France) with thinkers like Descartes, Leibniz, and Spinoza. Key tenets include:
  • Belief in innate ideas.
  • Emphasis on deduction as the primary mode of inference.
  • Concerned with the origin and validity of human knowledge, trusting reason as the source.
• Empiricism: Developed primarily in Great Britain with thinkers such as Locke, Berkeley, and Hume. Key tenets include:
  • The mind is born as a ‘blank slate’ (tabula rasa).
  • Knowledge is acquired through experience (senses).
  • Emphasis on induction, influenced by figures like Newton.
  • Also concerned with the origin and validity of human knowledge, trusting experience as the source.
  • Can lead towards relativism.

Hume: Impressions vs. Ideas in Human Knowledge

For Hume, both impressions and ideas are contents of the human mind. Following the empiricist doctrine, he maintained that there is nothing in the intellect that was not previously in the senses; all human knowledge originates from experience.

• Impressions: These are vivid and immediate perceptions provided by the senses, either externally (sensation) or internally (emotions, passions), experienced ‘now‘.
• Ideas: These are weaker perceptions, like copies or memories of past impressions. They are the ‘remembrance’ of an impression.

This distinction reiterates the empirical maxim: “There is nothing that is not derived from experience.”

Hume: Relations of Ideas vs. Matters of Fact

Hume distinguished between two types of propositions or objects of human reason:

• Relations of Ideas: These propositions (e.g., in geometry, algebra, arithmetic) are discoverable by the mere operation of thought, without dependence on what exists in the universe. They bear no relation to real existence. Sciences based on relations of ideas preserve universality and necessity; their statements are not verifiable by experience but are deductible according to rules established a priori. Denying them involves a contradiction.
• Matters of Fact: These propositions concern existence and experience. They inform us about the world (unlike tautologies). Their truth is established through experience and observation, and their contrary is always possible without contradiction. Establishing their truth is more problematic as it often relies on cause and effect.

Hume’s Critique of the Principle of Causality

The principle of causality claims that every event has a cause and necessarily produces an effect. This principle is fundamental for science and much of our reasoning about the world.

Hume, however, subjected this principle to empirical scrutiny. He argued that for this principle to be valid based on experience, it must be empirically justifiable. Yet, observing nature reveals only constant conjunction (one event regularly following another), not a necessary connection between cause and effect. We cannot find a sensory impression corresponding to this supposed necessary connection.

Hume concluded that our belief in the principle of causality stems not from reason or direct observation of necessity, but from a mental habit formed by repeatedly observing the temporal conjunction of events. It is the mind, through habit, that projects this idea of necessary connection onto events. Therefore, the principle is not based on objective reality but on the psychological habit of the observer.

Hume: Phenomenalism, Skepticism, and Relativism

Hume’s rigorous empiricism leads to several significant conclusions:

• Phenomenalism: Since we only have access to our perceptions (impressions and ideas), we are unable to find a certain basis for connections between them or for an external reality causing them. We only know phenomena (appearances). Hume believed the human mind is limited and cautioned against speculating about underlying realities (‘things-in-themselves’).
• Skepticism: One can be certain of one’s own impressions and ideas, but not of the external objects or underlying realities they supposedly represent. Our knowledge is limited to our perceptions. This leads to a mitigated skepticism about claims extending beyond immediate experience.
• Relativism: Since knowledge depends solely on individual sensory experience and perceptions, different individuals may have different, yet equally valid (from their perspective), understandings of the world. This challenges the notion of a single, objective truth accessible to all, suggesting truth becomes relative to the individual’s experience.

Hume’s Problem of Induction Explained

Induction is the process of reasoning from specific observations to broader generalizations or predictions about the unobserved. Hume identified a fundamental problem with justifying this process:

1. Scientists (and people in everyday life) observe patterns in the world and generalize from these observations (e.g., observing many white swans leads to the conclusion “All swans are white”).
2. However, such generalizations cannot be definitively verified because we cannot observe all possible instances (past, present, and future). We assume the future will resemble the past.
3. This assumption relies on the principle of the uniformity of nature.
4. But how do we justify this principle? If we try to justify it based on past experience (i.e., nature has been uniform *so far*), we are using induction.
5. This leads to a vicious circle or circular argument: to demonstrate the validity of induction, we must presuppose that induction itself is valid.

Hume concluded that induction is not based on reason but is a habit or custom, essential for practical life but lacking ultimate rational justification.

Hume’s Moral Emotivism: Feeling Over Reason

Hume rejects a purely rationalist basis for morality. He argues:

• Reason (knowledge) informs us about situations, facts, and consequences, but it cannot motivate action or produce moral distinctions on its own.
• It is feeling or sentiment (emotions like approval or disapproval) that guides our moral judgments and actions. Moral distinctions (virtue/vice, right/wrong) do not originate from reason alone.
• Hume distinguishes between errors of fact (ignorance about circumstances) and the nature of moral judgment itself, which arises from sentiment. Certain actions naturally arouse feelings of approval or disapproval in us.
• While human beings naturally pursue their own good (self-interest), Hume argues they also possess sentiments like sympathy, allowing them to feel pleasure at others’ happiness and pain at their suffering (altruism).
• Moral judgments arise from these shared human feelings. This view, where morality is founded on sentiment rather than reason, is called moral emotivism.

Hume’s Political Theory: Society and Government

Hume offered a pragmatic and empirical approach to politics:

• Rejection of Abstract Origins: He rejected theories of the divine origin of power and the historical reality of a foundational social contract. He argued that a formal pact requires pre-existing societal norms and structures, making it an unlikely origin point.
• Natural Origins of Society: The origin of society stems from natural human instincts, particularly sexual appetite and affection for offspring, which solidify within the family institution – the earliest form of social organization. Convenience and shared interests gradually expand social cooperation.
• Purpose of Government: Government arises later, not from a contract, but out of the practical necessity to regulate cohabitation, enforce justice (especially regarding property rights), and ensure stability as societies grow larger and more complex. Its primary end is utility and the common good.
• Role of Government: Governments derive legitimacy from their effectiveness in maintaining peace and order. They should be founded on principles that ensure stability and public benefit. Hume advocated for tolerance and respect for freedom of thought, belief, and expression.