Intuition
This source of knowledge is about the intuition conviction of certainty that sometime is experienced quite suddenly
For example, Capitalism is more efficient and productive than socialism. This is because I believe so and sure that is true without reason. Therefore knowledge based on intuition is sometimes unreliable and difficult to test. Therefore, the authors suggests that before accepting the claims, it should be assured that the claim is based on intuition not from some other sources of knowledge; sense of experience, reasoning, and authority, recognize that different persons’ intuitions conflict, and understand that intuition tells us to know something while knowing that intuitive experience does not means that it says true.