Understanding Knowledge: Ideas, Relations, and Facts

The Relationship Between Ideas

Ideas are the materials of knowledge, appearing in a specific order. This order depends on whether it's power, memory, or imagination that brings them to mind. Memory maintains the original momentum and position of ideas, while imagination combines them more freely. We can imagine fantastical creatures, like a centaur, but we remember a horse. Hume identifies a 'soft power' in human nature that associates ideas along three principles: similarity, spatiotemporal contiguity, and causation. "A picture naturally leads our thoughts to the original. The mention of one room in a building naturally introduces a question or comment about the others, and if we think of a wound, we can hardly refrain from thinking about the pain that followed."

Types of Knowledge

Hume divides knowledge into two types:

• Relations of Ideas: Knowledge governed by the principle of contradiction. These correspond to mathematics, geometry, algebra, and arithmetic, which are independent of the real world. For example, "a triangle has three angles" is true regardless of experience.
• Matters of Fact: Factual knowledge, guided by experience. Examples include: "The day is sunny," "Yesterday I went to the theater," or "The sun will rise tomorrow." This knowledge doesn't offer the same certainty as relations of ideas, as the opposite is always possible without contradiction.

Hume examines the nature of knowledge that allows us to predict future events beyond present sensory testimony or memory.