Locke and Hume: Understanding the Foundations of Knowledge

Locke's Theory of Knowledge

Locke's theory begins with the rejection of rationalist nativism. He argues against the existence of innate ideas or knowledge in the understanding. If such innate ideas existed, all individuals would possess them from the beginning of their existence, but this is not something we observe.

The understanding is more like a blank slate (tabula rasa).

Classes of Concepts and Ideas

When speaking of "idea", Locke refers to everything we know or perceive.

• Simple Ideas: These ideas cannot be broken down into others. They are necessarily imposed on the mind, which remains passive. They can be classified as:
  • Ideas of Sensation: These originate from outer experience. They are impressions produced on our external senses by external objects. Through them, we grasp the qualities of bodies, which can be of two types: primary (objective) and secondary (subjective).
  • Ideas of Reflection: These come from inner experience. The human mind has knowledge of its own acts.
  • Mixed Ideas: These originate from the combined data of sensation and reflection.
• Complex Ideas: These are formed by the human mind, where the mind is active. They can be of three classes:
  • Modes: Formed by combination.
  • Relationships: Formed by comparing one thing with another.
  • General Ideas: Formed by abstraction of characteristics common to a plurality of individuals.

Critique of Substance

Locke critiques the concept of substance. By substance, he means a collection of simple ideas that are united in a single subject. We perceive a set of feelings that are always attached to experience. We suppose that below those qualities, there is something that supports them, but we do not know it. The substance, the substrate of these qualities, is unknowable.

Hume's Content of the Mind

Hume's theory also starts from experience but proposes a different classification. He calls all acts and mental contents "perceptions" and identifies two classes of perceptions: impressions and ideas.

• An impression is the current and immediate perception grasped by the senses.
• Ideas are representations or copies left by impressions in the mind.

Impressions have greater vivacity and intensity than ideas. Impressions, in turn, can be of sensation and reflection. Both impressions and ideas can be simple or complex. Simple perceptions do not allow for separation, while complex ones are formed by grouping simple perceptions and can be divided into parts.

Association of Ideas

Simple ideas occur in accordance with associative laws:

• Similarity
• Contiguity in time and place
• Cause-effect relationship

The Principle of the Copy

Impressions are prior in time to ideas. If we want to know if an idea is true, we must check if this idea comes from some impression. If so, we are facing a real idea; otherwise, it will be a fictitious or false idea. This criterion is called the "principle of the copy." Hume used this principle to critically examine the main metaphysical ideas.