1898. If x's judgment is trustworthy . . .

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If x's judgment is trustworthy, it provides a proper basis for action.

To attack the propriety of a claim is to attack either the grounds on which it is made (i.e., its backing) or the credentials of the person making it. 

Trustworthiness = credibility

To be a possibility, in the sense of a possible solution to a problem, is to be a suggested solution entitled to respectful consideration (involving, at the very least, arguments against its selection) in any serious discussion of the problem to which it is relevant. 

If we make an assertion, we put forward a claim—a claim on the attention and to the belief of others. Therefore, if we make an assertion, we thereby commit ourselves to the claim that our assertion necessarily involves. If, then, our claim on the attention and to the belief of others is challenged, we have to be able to establish it—make it good, show that it was justifiable. This requires producing a justificatory argument for our assertion, whose merits we have claimed in making it, and which claim we now have to make good. 

The logical function of a warrant (W) is to authorize the move from data (D) to conclusion (C). Thus a warrant is, or functions as, an authority, i.e., the authority for moving from D to C. By the same token, the backing (B) of a warrant functions to ground the warrant's authority, i.e., its right and power to authorize (or license) a certain move. 

May 1999 (after rereading Stephen Toulmin's The Uses of Argument)