Opinion

An opinion is a person's ideas and thoughts towards something. It is an assessment, judgment or evaluation of something. An opinion is not a fact, because opinions are either not falsifiable, or the opinion has not been proven or verified. If it later becomes proven or verified, it is no longer an opinion, but a fact.

In economics, philosophy, or other social sciences, analysis based on opinions is referred to as normative analysis (what ought to be), as opposed to positive analysis, which is based on scientific observation (what materially is). In mathematics and logic there can be no opinions about some claims, equations, and arguments, because often these kinds of statements are either valid or invalid, and true or false, and not open to contradicting opinions.

Historically, the distinction of proven knowledge and opinion was articulated by some Ancient Greek philosophers. Plato's analogy of the divided line is a well-known illustration of the distinction between knowledge and opinion.