But in this same illusion discrimination is very necessary, since it ought to be nicely considered from what cause it occurs to the mind of the sleeper. For sometimes it happens from surfeit, sometimes from superfluity or infirmity of nature, sometimes from cogitation. And indeed when it has come to pass from superfluity or infirmity of nature, it is by no means to be viewed with alarm, since the mind is to be commiserated as having endured it unwittingly rather than as having done it.
But when the appetite of gluttony in taking food is carried beyond measure, and consequently the receptacles of the humours are loaded, the mind has therefore some guilt, yet not to the extent of prohibition from receiving the sacred mystery, or celebrating the solemnities of mass, when perchance a festival day demands it, or necessity itself requires the mystery to be exhibited by reason of there being no other priest in the place. For, if others competent to execute the mystery are present, an illusion caused by surfeit ought not to debar from receiving the sacred mystery, though immolation of the sacred mystery ought, as I think, to be humbly abstained from; provided only that foul imagination has not shaken the soul of the sleeper.
For there are some to whom the illusion for the most part so arises that their mind, though in the body which sleeps, is not defiled by foul imaginations. With regard to this, there is one case in which it is shown that the soul itself is guilty, not being free even from its own judgment; that is where, while it remembers having seen nothing when the body was asleep, it still remembers having fallen into lewdness when the body was awake. But, if the illusion arises in the soul of the sleeper from foul cogitation while he was awake, the mind's guilt is patent to itself.
For a man sees from what root that defilement proceeded, if he has endured unwittingly what he wittingly cogitated. But it is to be considered whether the cogitation ensued from suggestion, or delight, or sinful consent. For there are three ways in which all sin is accomplished; to wit, by suggestion, by delight, and by consent. Suggestion is through the devil, delight through the flesh, consent through the spirit; since, in the case of the first sin, the serpent suggested it, Eve, as the flesh, delighted in it, but Adam, as the spirit, consented to it.
And great discernment is needed, that the mind may sit as judge of itself to distinguish between suggestion and delight, between delight and consent. For, when the evil spirit suggests sin in the soul, if no delight in sin should follow, no sin is in any wise committed. But, when the flesh has begun to take delight, then sin has its commencement. But, if it sinks to deliberate consent, then sin is known to be completed. In suggestion therefore is the seed of sin, in delight its nutriment, in consent its completion.
And it often happens that what the evil spirit sows in the thought the flesh draws into delight, and yet the mind does not consent to this delight. And, while the flesh cannot be delighted without the soul, still the mind, though struggling against the pleasures of the flesh, is in some way bound against its will in carnal delight, so as by force of reason to protest against it and not consent to it, and yet to be bound by the delight, but still to groan exceedingly for being bound.
Whence even that chief soldier of the heavenly army groaned, saying, I see another law in my members fighting against the law of my mind, and bringing me into captivity to the law of sin which is in my members. Yet, if he was a captive, he did not fight. But he did fight too, and therefore he was not a captive. And therefore he fought by the law of the mind, which the law which is in the members fought against. If he thus fought, he was not a captive. Behold then man is, so to speak, both a captive and free: free with regard to the righteousness which he loves; a captive with regard to the delight which he endures unwillingly.
Source: Register of Letters (New Advent)