Of the law of God you must draw your reasons in showing by the scripture that the thing which he thinketh God biddeth by his angel, God hath by his own mouth forbidden.  And that is, you know well, in the case that we speak of, so easy to find that I need not to rehearse it to you.  For among the Ten Commandments there is plainly forbidden the unlawful killing of any man, and therefore of himself, as (St. Austine saith) all the church teacheth, unless he himself be no man.

Vincent:  This is very true, good uncle, nor will I dispute upon any glossing of that prohibition.  But since we find not the contrary but that God may dispense with that commandment himself, and both license and command also, if he himself wish, any man to go kill either another man or himself, this man who is now by such a marvellous vision induced to believe that God so biddeth him, and therefore thinketh himself in that case discharged of that prohibition and charged with the contrary commandment—­with what reason can we make him perceive that his vision is but an illusion and not a true revelation?

Anthony:  Nay, Cousin Vincent, you shall in this case not need to ask those reasons of me.  But taking the scripture of God for a ground for this matter, you know very well yourself that you shall go somewhat a shorter way to work if you ask this question of him:  Since God hath forbidden once the thing himself, though he may dispense with it if he will, yet since the devil may feign himself God and with a marvellous vision delude one, and make as though God did it; and since the devil is also more likely to speak against God’s commandment than God against his own; you shall have good cause, I say, to demand of the man himself whereby he knoweth that his vision is God’s true revelation and not the devil’s false delusion.

Vincent:  Indeed, uncle, I think that would be a hard question to him.  Can a man, uncle, have in such a thing even a very sure knowledge of his own mind?

Anthony:  Yea, cousin, God may cast into the mind of a man, I suppose, such an inward light of understanding that he cannot fail but be sure thereof.  And yet he who is deluded by the devil may think himself as sure and yet be deceived indeed.  And such a difference is there in a manner between them, as between the sight of a thing while we are awake and look thereon, and the sight with which we see a thing in our sleep while we dream thereof.

Vincent:  This is a pretty similitude, uncle, in this thing!  And then is it easy for the monk that we speak of to declare that he knoweth his vision for a true revelation and not a false delusion, if there be so great a difference between them.

Anthony:  Not so easy yet, cousin, as you think it would be.  For how can you prove to me that you are awake?

Vincent:  Marry, lo, do I not now wag my hand, shake my head, and stamp with my foot here on the floor?