Full Idea
What is supposed to identify the person of logos from the one without is the commitment to giving reasons explaining why one opinion is superior to another.
Clarification
'Logos' is the broad Greek concept of human reasoning
Gist of Idea
The hallmark of a person with logos is that they give reasons why one opinion is superior to another
Source
David Roochnik (The Tragedy of Reason [1990], Intro. 17)
Book Reference
Roochnik,David: 'The Tragedy of Reason: the Platonic logos' [Routledge 1990], p.17