And then a sudden thought comes to him.

Why not go on?
Why not put it to be proof?
Why not win his wager?
Tita is thoughtless; but it would be madness in anyone to think her vile.

It was madness in _him_ a moment since to dream of her being alone in that small, isolated arbour with Hescott.

Much as he may revolt--as he does revolt--from this abominable wager he has entered into, surely it is better to go on with it and bring it to a satisfactory end for Tita than to "cry off," and subject her to scoffs and jeers from her adversary.
"Let us go on," says he quietly.

"I shall win my bet.