In epistemology, philosophers use the term ‘belief’ to refer to personal attitudes associated with true or false ideas and concepts. However, ‘belief’ does not require active introspection and circumspection. For example, we never ponder whether or not the sun will rise. We simply assume the sun will rise. Since ‘belief’ is an important aspect of mundane life, according to the Stanford Encyclopedia of Philosophy, the question that must be answered is, “how a physical organism can have beliefs” (http://plato.stanford.edu/entries/belief/).
Epistemology is concerned with delineating the boundary between justified belief and opinion, and involved generally with a theoretical philosophical study of knowledge. The primary problem in epistemology is to understand exactly what is needed in order for us to have knowledge. In a notion derived from Plato's dialogue Theaetetus, where the epistemology of Socrates (Platon) most clearly departs from that of the sophists, who at the time of Plato seem to have defined knowledge as what is here expressed as "justified true belief". The tendency to translate from belief (here: doxa - common opinion) to knowledge (here: episteme), which Plato (e.g. Socrates of the dialogue) utterly dismisses, results from failing to distinguish a dispositive belief (gr. 'doxa', not 'pistis') from knowledge (episteme) when the opinion is regarded true (here: orthé), in terms of right, and juristically so (according to the premises of the dialogue). Which was the task of the rhetors to prove. Plato dismisses this possibility of an affirmative relation between belief (i.e. opinion) and knowledge even when the one who opines grounds his belief on the rule, and is able to add justification (gr. logos: reasonable and necessarily plausible assertions/evidence/guidance) to it. It is important to keep in mind that the sort of belief in the context of Theaetetus is not derived from the theological concept of belief, which is pistis, but doxa, which in theological terms refers to acceptance in the form of praise and glory.
Strangely, or not, Plato has been credited for the "justified true belief" theory of knowledge, even though Plato in the Theaetetus (dialogue) elegantly dismisses it, and even posits this argument of Socrates as a cause for his death penalty . Among American epistemologists, Gettier (1963) and Goldman (1967), have questioned the "justified true belief" definition, and challenged the "sophists" of their time.