Evidence

Evidence is the information used to support a specific proposition or claim. It serves as an indication that a statement might be true. The exact role of evidence changes depending on the field of study. In epistemology, which is the study of knowledge, evidence justifies beliefs. It makes it rational for a person to hold a certain mental attitude. For example, seeing a tree provides perceptual evidence for the belief that a tree exists. In this context, evidence is often viewed as a private mental state.

In the field of science, evidence functions differently. Scientific evidence is information gained through the scientific method. It acts as a neutral arbiter to settle debates between competing theories. This information can either confirm or disconfirm a specific scientific hypothesis. For instance, measurements of the orbit of Mercury provided evidence for Einstein's theory of general relativity. Philosophers of science often prefer to see evidence as verifiable information. They focus on observable physical objects or events rather than private thoughts. This ensures that evidence is public and can be shared by different scientists.

Different disciplines use different types of evidence to reach conclusions. In the legal system, evidence is used to establish or refute claims in a case. This can include testimony from people or documentary evidence. Physical evidence is also a vital part of legal proceedings.

In phenomenology, evidence is viewed as intuitive knowledge. Some thinkers assume this provides indubitable access to the truth. However, the different definitions of evidence across fields can be incompatible. It is difficult to find a single concept that links a bloody knife in a crime scene to a private mental experience. This suggests there may not be one unitary definition for evidence.

Philosophers have identified several characteristics that make an argument or proof more evident. A researcher named Riofrio identified ten specific characteristics of what is evident. Six of these are intrinsic, meaning they belong to the truth itself. These include being coherent with other truths and being based on necessary reasoning. The simplest truths are often the most evident because they are self-explanatory. The other four characteristics are subjective or external. These include the sense of certainty the evidence provides to the knower. Evident truths also appear natural, effortless, and widely shared through common sense.

In the 20th century, scholars began studying the "evidential relation." This is the study of how evidence and a supported statement are connected. One major theory is the probabilistic approach, also called Bayesian confirmation theory. This theory suggests that evidence is valid if it increases the probability of a hypothesis. For example, smoke is evidence of a fire because they usually occur together. However, critics argue this approach can be too liberal. They note that finding a nickel in a pocket increases the probability that all coins are nickels, but it lacks a lawful connection.

Another theory is hypothetico-deductivism, which is a non-probabilistic approach. This view states that evidence consists of the observational consequences of a hypothesis. If a theory is true, it should predict certain observable results. This method is common in experimental science. However, it faces the problem of auxiliary assumptions. To connect a hypothesis to an observation, scientists must include assumptions about lighting, location, or chemistry. This turns the relationship into a complex connection between evidence, the hypothesis, and these extra assumptions.

A third way to look at this is the positive-instance approach. This approach claims an observation is evidence if it describes a positive instance of a universal statement. For example, seeing one white swan is evidence for the rule that all swans are white. This uses formal logic to show how an observation fits a broader rule. One problem with this view is the requirement for a shared vocabulary. Many scientific theories involve objects like electrons that are not directly observable. This makes it hard to use the positive-instance approach for all types of science.

Many important thinkers have shaped our understanding of these concepts. Aristotle and the phenomenologists studied the nature of evident truths. In more modern times, Bertrand Russell and W.V.O. Quine have been influential. The logical positivists also played a major role in these discussions. Today, evidence remains central to many fields. It is used in history, journalism, and everyday discourse. It provides the foundation that allows different branches of scientific knowledge to flourish and grow.