The Story of Modern Epistemology

How do we know what we know? That's what Descartes asked. His first conclusion: I think therefore I am. In other words, there are thoughts that one is conscious of, and that proves that one exists. The problem: where to go from there? That's where Descartes faltered. David Hume came along and said: how do we even know about causality? All we know is that one thing follows another thing. Immanuel Kant came along and shook things up: causality must exist in our minds at the very least because we cannot conceive of a world that doesn't exist without causality. If causality didn't exist, our minds wouldn't be able to function.