And that ordeal, though method or detail was unknown to me, I was prepared to undertake.

This was one of those occasions when a man must undertake, blindfold, ways that may lead to torture or death, or unknown terrors beyond.

But, then, a man--if, indeed, he have the heart of a man--can always undertake; he can at least make the first step, though it may turn out that through the weakness of mortality he may be unable to fulfil his own intent, or justify his belief in his own powers.

Such, I take it, was the intellectual attitude of the brave souls who of old faced the tortures of the Inquisition.
But though there was no immediate fear, there was a certain doubt.

For doubt is one of those mental conditions whose calling we cannot control.
The end of the doubting may not be a reality to us, or be accepted as a possibility.