evidence information bearing on the truth or falsity of a proposition. In philosophical discussions, a person’s evidence is generally taken to be all the information a person has, positive or negative, relevant to a proposition. The notion of evidence used in philosophy thus differs from the ordinary notion according to which physical objects, such as a strand of hair or a drop of blood, counts as evidence. One’s information about such objects could be evidence in the philosophical sense. The concept of evidence plays a central role in our understanding of knowledge and rationality. According to a traditional and widely held view, one has knowledge only when one has a true belief based on very strong evidence. Rational belief is belief based on adequate evidence, even if that evidence falls short of what is needed for knowledge. Many traditional philosophical debates, such as those about our knowledge of the external world, the rationality of religious belief, and the rational basis for moral judgments, are largely about whether the evidence we have in these areas is sufficient to yield knowledge or rational belief. The senses are a primary source of evidence. Thus, for most, if not all, of our beliefs, ultimately our evidence traces back to sensory experience. Other sources of evidence include memory and the testimony of others. Of course, both of these sources rely on the senses in one way or another. According to rationalist views, we can also get evidence for some propositions through mere reason or reflection, and so reason is an additional source of evidence. The evidence one has for a belief may be conclusive or inconclusive. Conclusive evidence is so strong as to rule out all possibility of error. The discussions of skepticism show clearly that we lack conclusive evidence for our beliefs about the external world, about the past, about other minds, and about nearly any other topic. Thus, an individual’s perceptual experiences provide only inconclusive evidence for beliefs about the external world since such experiences can be deceptive or hallucinatory. Inconclusive, or prima facie, evidence can always be defeated or overridden by subsequently acquired evidence, as, e.g., when testimonial evidence in favor of a proposition is overridden by the evidence provided by subsequent experiences. See also EPISTEMOLOGY , SKEPTICIS. R.Fe.