Self-evidence

In epistemology, the study of knowledge, a self-evident proposition is an idea we know is true just by thinking about it. We don’t need proof or extra facts; our normal thinking can understand it.

Some people who study knowledge think nothing can be self-evident. But many believe we can know some things are true just by thinking about them. For example, we know we are conscious and that we have free will. But we can’t be sure about someone else’s thoughts or choices in the same way.

One example of a self-evident idea is: “A finite whole is greater than, or equal to, any of its parts.” This makes sense when we think about it, without needing more details or proof.

Analytic propositions

Some people say that a self-evident idea cannot be untrue because it would be confusing. Others say the same about an analytic proposition. But these two ideas are not the same. An analytic proposition is not always self-evident.

If you understand and believe a self-evident idea, you don’t need proof. The same is true for knowing that the opposite would be confusing—you also don’t need proof. The way confusion works is different for self-evident ideas and analytic propositions.

Not every analytic proposition is self-evident, and some think not all self-evident ideas are analytic. For example, knowing that you are aware and thinking is self-evident.

Other uses

When people say something is "self-evident," they mean it is very clear.

In deeper thinking about knowledge, the idea is stricter.

Some important ideas about right and wrong may feel clear and true without needing proof. For example, Alexander Hamilton mentioned ideas like "The means ought to be proportioned to the end" as clear truths in his writing called the Federalist No. 23. The United States Declaration of Independence says, "We hold these Truths to be self-evident, that all men are created equal..." Even though these ideas feel clear, some people debate if they truly need no proof.

In mathematics, a self-evident statement is one that doesn’t need a proof because it is clear on its own. Sometimes these are called axioms. Other statements prove themselves without extra help.