Prima Facie Evidence

A reader inquires:

     Is 'prima facie' evidence something with self-evident contextual
     significance or a evidence that constitutes some sort of
     transcendental first principle? I am having some trouble with this
     concept.

The Latin phrase means 'on the face of it,' or 'at first glance.'  Prima facie evidence, then, is evidence that makes a strong claim on our credence but can perhaps be rebutted or overturned. The term is   used in the law to refer to evidence which, if uncontested, would establish a fact or raise a presumption of a fact. If you have the victim's blood on your hands, and you are acting nervous, and are seen   running from the crime scene with passport in pocket, and have been recently overheard threatening the life of the victim, then that adds up to a strong prima facie case for your having committed the crime.  But these bits of evidence, even taken together, are not conclusive.

Philosophers use the term in roughly the same way. For example, a prima facie duty is a duty which, in the absence of conflicting duties, is our actual obligation. If I promise to meet you tomorrow at noon at the corner of Fifth and Vermouth to discuss epistemology, then, so promising, I incur the duty to meet you then and there. But if my wife becomes ill in the meantime then my duty reverts to her care. The prima facie duty to meet you is defeated or overridden by the duty to care for my wife.

Or a philosopher might speak of the prima facie evidence of memory. My seeming to remember having mailed my tax return to the Infernal  Revenue Service is good prima facie evidence of my having mailed it,  but it is defeasible evidence.

Prima facie evidence should not be confused with self-evidence. Prima facie evidence is defeasible while (objective) self-evidence is not.