A posteriori cognition is one way in which humans understand the world. A person understands something a posteriori if their ideas of it come from specific experiences. For example, a person knows their favorite food based on their experiences eating it. Kant argues that previous conceptions of moral laws relied too heavily on a posteriori reasoning, which he felt was a less reliable way of proving their existence. A priori refers to intuitive knowledge and reasoning. For example, we intuitively know we are capable of rational thought. Kant argues that rational beings can understand morality a priori.

Analytic and synthetic distinction refer to types of human judgment that help us understand if something is true or false. Analytic distinctions support our intuitive understanding of whether an idea is true or false. People can engage with them without any specific experiences. This means, grammatically speaking, the predicate describes the subject. An example of analytic distinction is: “Children are young,” because the predicate (are) connects to an objective fact about children. Someone can understand children are young without any hands-on experience with them.

Conversely, synthetic distinction requires additional context before it can be considered true or false. This context is usually gained from direct experience with an idea.