It did not matter whether it were real to others or not, it would be too real to him.

He could never get rid of the sensation; it would haunt him and oppress him for the rest of his life, and he should have no peace.
How could it, if it were not a real thing?
Even the priests said that the spirits of dead men did not come back to earth; how much more impossible must it be in Marzio's view, since he denied that man had a soul.

It would then only be the effect of his imagination recalling constantly the past deed, and a thing which only existed in imagination did not exist at all.

If it did not exist, it could not be feared by a sensible man.

Consequently there was nothing to fear.
The conclusion contradicted the given facts from which he had argued, and the chiseller was puzzled.