The button is always on the Bishop's foil.
He never sends the rapier home.

And no doubt that is the reason that his companion, with "his sudden healthy vehemence" did drive his weapon home into life--and started for Australia.
Mr.Sludge, the medium, excuses his imposture, and then thinks "it may not altogether be imposture.

For all he knows there may really be spirits at the bottom of it.

He never meant to cheat; yet he did cheat.
Yet, even if he lied, lies help truth to live; and he must live himself; and God may have made fools for him to live on;" and many other are the twists of his defence.

The poem is as lifelike in its insight into the mind of a supple cheat as it is a brilliant bit of literature; but Browning leaves the matter unconcluded, as he would not have done, I hold, had he been writing poetry.