An argumentative claim must always be supported by evidence, which can take the form of facts that can be verified, debated, corroborated, checked, and evaluated, either by logical means or by empirical analysis (observation, analysis, demonstrability). It is no easy task to define a fact, but, in rough terms, it is an occurrence that is actual and present (or that is has been both at some point) and that can be said to be a state of things regarding a problem or an object of research.
