Evidentialism is a stance or theory of epistemology, which holds, for example, that belief in the truth of a proposition is justified, only to the extent that evidence demonstrates the truth of the proposition. In other words, belief is only as sound as the evidence upon which it is founded.

Mortimer Adler argues that the very nature of full belief implies evidentialism. He concludes that belief is an attitude which is subject to the demands of evidence, so that it is not consistent to believe any proposition without evidence. Adler's argument is an example of evidentialism.

In contrast, non-evidentialism argues that beliefs can be held without rational evidence. Fideism, as an example of non-evidentialism, holds that religious belief must be based on belief alone.

There is a lot of empirical evidence that, in many cases, the human mind is not naturally inclined to follow evidentialism. Cognitive dissonance is one example of this natural resistance.

See also List of cognitive biases