How does a contradiction differ from a logically true proposition?

In logic, a contradiction and a logically true proposition (often called a tautology) represent opposite ends of the truth-value spectrum.

• Logically True Propositions: A proposition is logically true if it is true in all possible worlds and cannot be false. These statements, such as "It is raining now or it is not raining now," instantiate a law of logic and are considered necessary truths. In a truth table, a tautology will result in a value of "true" for every possible combination of truth-values assigned to its components.12

• Contradictions: A contradiction is a statement that cannot be true. According to the law of noncontradiction, contradictory propositions cannot both be true at the same time and in the same sense. While a tautology is true by definition or logical structure, a contradiction is inherently false because it asserts and denies the same thing simultaneously.34

Essentially, a logically true proposition is necessarily true, whereas a contradiction is necessarily false.14