 Crucial to any theory in the ethics of belief—and especially an Evidentialist theory—will be some account of the nature of evidence itself. Some philosophers construe evidence in terms of demonstrative proof, others in terms of objective and/or subjective probability, and others simply in terms of anything that belief is responsive to (see the entry on  evidence).  A fully articulate Evidentialism will also provide an account of how evidence supports belief (see the entry on the  epistemic basing relation),  and of what it is to have or possess such evidence.