One can be told purported factual information from a number of sources including other people (often authority figures), written texts, and other recorded media. Inevitably, not all claims that one may come across will be entirely accurate, so it is necessary to figure out for oneself what to believe and what not to believe. Purported truths fall into several categories, some of which are as follows:
- Purported personal experiences or autobiographical details, such as reports of events by someone claiming to be an eyewitness.
- Purported details of current events, such as what one often finds in a newspaper or television news report.
- Purported historical truth, such as what one might find in a history book or what a historian might claim to be true.
- Purported scientific truth, such as what one might find in a science book or what a scientist might claim to be true.
- Purported revealed divine or dogmatic truth, such as what one might find in a book of holy scriptures or what a person of faith might claim to be true.
In order for one to be epistemically justified to believe in a claim, all of the following factors must be met:
- The content of the claim is coherent with all of one’s existing epistemically justified beliefs, which must ultimately be coherent with personally observed facts about how nature works.
- The content of the claim is naturalizable, which means that it can be understood as resulting from natural laws, whether these laws are known to exist or not.
- The source of the claim has earned credibility in the subject area that the claim relates to because it has a good track record. The credibility of a claim is stronger or weaker based on the track record of the source that provided the claim, all other factors being equal. The credibility of a claim is stronger if it comes from a source that has a history of providing accurate information and of not providing disinformation, which is a claim shown to be false due to the prevalence of counterevidence. Conversely, if a claim comes from a source that does not have a history of providing accurate claims and instead has a history of providing disinformation, then the credibility of this claim is weaker.
- The source of the claim is trusted by other sources that also have good track records in the subject area that the claim relates to. A good way to identify this is through official credentials or membership in a professional organization that has its own credibility.
- The one evaluating the claim has a certain understanding of the process through which the claimant came to believe in the idea behind this claim, and this process is plausible because it only involves the use of senses and mental facilities that people are known to have. Any claim must come from an idea in someone’s mind, and this person needs to have evidence for this idea in order for a claim based on it to be epistemically justified.
If one believes in a claim that meets some, but not all, of the aforementioned conditions then this belief is at a higher epistemic level than blind faith but a lower epistemic level than justification. This epistemic level is presumption, which is where one comes to a reasonable conclusion given limited evidence and where other conclusions, such as not accepting the claim, might also seem reasonable. If few or none of these conditions are met for a given claim, then one must have faith to believe in it.