Full Idea
Unfortunately for the logos there is no argument that can, without begging the question, establish the goodness of argumentation.
Clarification
'Logos' is the Greek ideal of pure reason
Gist of Idea
Unfortunately for reason, argument can't be used to establish the value of argument
Source
David Roochnik (The Tragedy of Reason [1990], p.106)
Book Reference
Roochnik,David: 'The Tragedy of Reason: the Platonic logos' [Routledge 1990], p.106