Evidence in its broadest sense includes everything that is used to determine or demonstrate the truth of an assertion. Giving or procuring evidence is the process of using those things that are either a) presumed to be true, or b) were themselves proven via evidence, to demonstrate an assertion's truth. Evidence is the currency by which one fulfills the burden of proof.

There are many issues that surround evidence, making it the subject of much discussion and disagreement. In addition to its subtle nature, evidence plays an important role in many academic disciplines, including science and law, adding to the discourse surrounding it.

An important distinction in the field of evidence is that between circumstantial evidence and direct evidence, or evidence that suggests truth as opposed to evidence that directly proves truth. Many have seen this line to be less-than-clear and significant arguments have arisen over the difference.

Burden of proof

main: Burden of proof The burden of proof is the burden of providing sufficient evidence to shift a conclusion from an oppositional opinion. Whoever does not carry the burden of proof carries the benefit of assumption. Whoever bears the burden of proof must present sufficient evidence to move the conclusion to their own position. The burden of proof must be fulfilled both by establishing positive evidence and negating oppositional evidence.

There are two primary burden-of-proof considerations:
1) The question of on whom the burden rests.
2) The question of the degree of certitude the proof must support. This depends on both the quantity and quality of evidence and the nature of the point under contention. Some common degrees of certitude include the most probable event, reasonable doubt, and beyond the shadow of a doubt.

Conclusions (from evidence) may be subject to criticism from a perceived failure to fulfill the burden of proof.

Problems in evidence

The theory of evidence is a field wrought with dispute. Many of these disputes stem from the limits of human knowing, a field known as epistemology. Possibly the most salient question of evidence is how, if, and what, one can know. (Or, in other words, the question is to what extent is it even possible to fulfill the burden of proof.) This is the question of evidence's limits. Some believe all evidence to be circumstantial, denying the possibility of direct evidence.

To help deal with this problem, many fields have found it useful to talk about levels of evidence and certainty, particularly the field of law.

Evidence in science

main: Scientific evidence In scientific research evidence is accumulated through observations of phenomena that occur in the natural world, or which are created as experiments in a laboratory. Scientific evidence usually goes towards supporting or rejecting a hypothesis.

One must always remember that the burden of proof is on the person making the claim. Within science, this translates to the burden resting on presenters of a paper, in which the presenters argue for their specific findings. This paper is placed before a panel of judges where the presenter must defend the thesis against all challenges.