Stating assertions in a way that permits them to be tested for truth or falsehood

The extent to which a scientific assertion is amenable to systematic probes, any one of which could negate the scientist's expectations.

In science and the philosophy of science, falsifiability, contingency, and defeasibility are roughly equivalent terms referring to the property of empirical statements that they must admit of logical counterexamples. This stands in contradistinction to formal and mathematical statements that may be tautologies, that is, universally true by dint of definitions, axioms, and proofs. Some philosophers and scientists, most notably Karl Popper, have asserted that no empirical hypothesis, proposition, or theory can be considered scientific if it does not admit the possibility of a contrary case.