Other forms: apodictically
Anything apodictic is certain: it cannot be disputed. The existence of gravity is apodictic.
This word comes from a Greek verb meaning to demonstrate, and it applies to things that have been demonstrated beyond a shadow of a doubt. An apodictic statement is absolutely, completely, unquestionably true. Usually, this applies to the logic of a statement or argument that is airtight. Lawyers try to make apodictic arguments: flawless arguments. If something is apodictic, there’s no point in questioning it. “Slavery is wrong” is an apodictic statement.