In epistemology, evidence is what justifies beliefs or what makes it rational to hold a certain doxastic attitude. For example, a perceptual experience of a tree may act as evidence that justifies the belief that there is a tree. In this role, evidence is usually understood as a private mental state. Important topics in this field include the questions of what the nature of these mental states is, for example, whether they have to be propositional, and whether misleading mental states can still qualify as evidence.
In phenomenology, evidence is understood in a similar sense. Here, however, it is limited to intuitive knowledge that provides immediate access to truth and is therefore indubitable. In this role, it is supposed to provide ultimate justifications for basic philosophical principles and thus turn philosophy into a rigorous science. However, it is highly controversial whether evidence can meet these requirements.
In philosophy of science, evidence is understood as that which confirms or disconfirms scientific hypotheses. Measurements of Mercury's "anomalous" orbit, for example, are seen as evidence that confirms Einstein's theory of general relativity. In order to play the role of neutral arbiter between competing theories, it is important that scientific evidence is public and uncontroversial, like observable physical objects or events, so that the proponents of the different theories can agree on what the evidence is. This is ensured by following the scientific method and tends to lead to an emerging scientific consensus through the gradual accumulation of evidence. Two issues for the scientific conception of evidence are the problem of underdetermination, i.e. that the available evidence may support competing theories equally well, and theory-ladenness, i.e. that what some scientists consider the evidence to be may already involve various theoretical assumptions not shared by other scientists. It is often held that there are two kinds of evidence: intellectual evidence or what is self-evident and empirical evidence or evidence accessible through the senses.

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