Keltham should have thought of his response to that before he walked in.
"I should have thought of my response to that question before you entered, sorry again that I didn't... you can definitely first-order disagree, how likely you are to shift my first-order opinions by argument is a separate question."
"If you solved six out of seven problems from yesterday on your own before you walked in, and what I thought was the middle third only got five while trying on their own, that would - well, frankly, it would surprise me enough that I'd want further verification with more tests, but it would de-convince me of my current opinion, at least."