The document discusses different theories of knowledge, including the objective theory and conception theory. The objective theory asserts that an external world exists independently of our perceptions. The conception theory holds that knowledge of universals comes from repeated sensations stored in memory. Other discussed sources of knowledge include customs, traditions, sense perception, intuition, and reason. Philosophers have debated the limits of human knowledge and whether true knowledge is possible given barriers like biases, logical fallacies, and propaganda.