Dredge laughed, but not unkindly. “My dear Archie, your father wasn’t one of the kind who bother to defend their case. Men like him are the masters, not the servants, of their theories. They respect an idea only as long as it’s of use to them; when it’s usefulness ends they chuck it out. And that’s what your father would have done.”

Archie reddened. “Don’t you assume a good deal in taking it for granted that he would have had to in this particular case?”

Dredge reflected. “Yes: I was going too far. Each of us can only answer for himself. But to my mind your father’s theory is refuted.”

“And you don’t hesitate to be the man to do it?”

“Should I have been of any use if I had? And did your father ever ask anything of me but to be of as much use as I could?”

It was Archie’s turn to reflect. “No. That was what he always wanted, of course.”

“That’s the way I’ve always felt. The first day he took me away from East Lethe I knew the debt I was piling up against him, and I never had any doubt as to how I’d pay it, or how he’d want it paid. He didn’t pick me out and train me for any object but to carry on the light. Do you suppose he’d have wanted me to snuff it out because it happened to light up a fact he didn’t fancy? I’m using his oil to feed my torch with: yes, but it isn’t really his torch or mine, or his oil or mine: they belong to each of us till we drop and hand them on.”

Archie turned a sobered glance on him. “I see your point. But if the job had to be done I don’t see that you need have done it from his chair.”

“There’s where we differ. If I did it at all I had to do it in the best way, and with all the authority his backing gave me. If I owe your father anything, I owe him that. It would have made him sick to see the job badly done. And don’t you see that the way to honour him, and show what he’s done for science, was to spare no advantage in my attack on him—that I’m proving the strength of his position by the desperateness of my assault?” Dredge paused and squared his lounging shoulders. “After all,” he added, “he’s not down yet, and if I leave him standing I guess it’ll be some time before anybody else cares to tackle him.”