One of the various general forms of argument employed in
   probable as distinguished from demonstrative reasoning, -- denominated
   by Aristotle to`poi (literally, places), as being the places or sources
   from which arguments may be derived, or to which they may be referred;
   also, a prepared form of argument, applicable to a great variety of
   cases, with a supply of which the ancient rhetoricians and orators
   provided themselves; a commonplace of argument or oratory.