Full Idea
The pragmatist says 'That's so' or 'that's true' are not just 'pro-sentential', but carry with them the thought that evidence does currently speak in favour of the statement asserted, and the prediction that it will continue to speak in favour.
Clarification
'Pro-sentential' use just refers back to a previous sentence
Gist of Idea
'That's true' doesn't just refer back to a sentence, but implies sustained evidence for it
Source
Cheryl Misak (Pragmatism and Deflationism [2007], 3)
Book Reference
'New Pragmatists', ed/tr. Misak,Cheryl [OUP 2009], p.77
A Reaction
This is a very nice point made by a pragmatist against the flimsy view of truth held by various deflationary views. You ought to believe what is true, and stand by what you hold to be true.