(no subject)
Relations of ideas is knowledge gained without experience, like the truths of rationality. They are certain truths, but they tell us nothing about the world. Matters of fact is knowledge that comes from experience. This knowledge gives us truth about the world but this truth can never be certain.
Man is flawed. Our senses deceive us. So how can we trust them if they do not show us the truth? Our knowledge about certain truths are not concrete, since some experience is universal and only limited within the factors that not only govern ourselves, but these same factors govern the world. But what governs the world? God? Pure science? Again, man is not certain, since the way we perceive the world is continuously flawed. No one knows anything for certain.