forum 7: week of 27 Feb - pragmatic encroachment

I think I rather agree with (2), almost unreservedly. And (3) does seem pragmatically straight-forward. But I cannot seem to make the three statements lead directly to the conclusion reached. They seem to me to lead to a justification in -doing- but not a difference in -knowing-. (1) doesn't lead to an alteration of knowledge, but an alteration of surety beyond knowledge. "Do you know that?" "Yes." "Are you SURE?" "Sure ENOUGH." is not changed to "Are you SURE?" "You're right, I don't know." It's rather "Are you SURE?" "No, I'm not sure, but I -think- so." I'm not sure (pun not intended) if it could be more convincing with a bit of rewording, though.