Self-evidence

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In epistemology, a self-evident proposition is one that is known to be true by understanding its meaning without proof.

Some epistemologists deny that any proposition can be self-evident. For most others, the belief that oneself is conscious is considered to be self-evident. However, one's belief that someone else is conscious is not epistemically self-evident.

The following metaphysical propositions are often said to be self-evident:

A finite whole is greater than any of its parts.
It is impossible for the something to be and not be at the same time in the same manner.

Certain forms of argument from self-evidence are considered fallacious or abusive in debate. For example, if a proposition is claimed to be self-evident, it is an argumentative fallacy to assert that disagreement with the proposition indicates misunderstanding of it.

Contents

1 Analytic propositions
2 Other uses

2.1 Informal speech
2.2 Moral propositions

Analytic propositions

It is sometimes said that a self-evident proposition is one whose denial is self-contradictory. It is also sometimes said that an analytic proposition is one whose denial is self-contradictory. But these two uses of the term self-contradictory mean entirely different things. A self-evident proposition cannot be denied without knowing that one contradicts oneself (provided one actually understands the proposition). An analytic proposition cannot be denied without a contradiction, but one may fail to know that there is a contradiction because it may be a contradiction that can be found only by a long and abstruse line of logical or mathematical reasoning. Most analytic propositions are very far from self-evident. Similarly, a self-evident proposition need not be analytic: my knowledge that I am conscious is self-evident but not analytic.

An analytic proposition, however long a chain of reasoning it takes to establish it, ultimately contains a tautology, and is thus only a verbal truth: a truth established through the verbal equivalence of a single meaning. For those who admit the existence of abstract concepts, the class of non-analytic self-evident truths can be regarded as truths of the understanding--truths revealing connections between the meanings of ideas.

Other uses

Claims of self-evidence also exist outside of epistemology.

Informal speech

In informal speech, self-evident often merely means obvious, but the epistemological definition is more strict.

Moral propositions

Moral propositions can also be said to be self-evident. For example, Alexander Hamilton cited the following moral propositions as self-evident in the Federalist #31:

The means ought to be proportioned to the end.
Every power ought to be commensurate with its object.
There ought to be no limitation of a power destined to effect a purpose which is itself incapable of limitation.

A famous claim of the self-evidence of a moral truth is in the U.S. Declaration of Independence, which states, We hold these Truths to be self-evident, that all men are created equal.... Philosophically, that proposition is not necessarily self-evident, and the subsequent propositions surely are not. Nevertheless, many would agree that the proposition we ought to treat subjects known to be equal in a certain sense equally in regard to that sense is morally self-evident. Thus, as Thomas Jefferson proposed, one can hold the propositions to be self-evident as the basis for practical, even revolutionary, behaviors.

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