The Cloud of Unknowing, ed. by Evelyn Underhill, , at sacred-texts.com
How a man shall know when his thought is no sin; and if it be sin, when it is deadly and when it is venial.
BUT it is not thus of the remembrance of any man or woman living in this life, or of any bodily or worldly thing whatsoever that it be. For why, a naked sudden thought of any of them, pressing against thy will and thy witting, although it be no sin imputed unto thee—for it is the pain of the original sin pressing against thy power, of the which sin thou art cleansed in thy baptism—nevertheless yet if this sudden stirring or thought be not smitten soon down, as fast for frailty thy fleshly heart is strained thereby: with some manner of liking, if it be a thing that pleaseth thee or p. 108 hath pleased thee before, or else with some manner of grumbling, if it be a thing that thee think grieveth thee, or hath grieved thee before. The which fastening, although it may in fleshly living men and women that be in deadly sin before be deadly; nevertheless in thee and in all other that have in a true will forsaken the world, and are obliged unto any degree in devout living in Holy Church, what so it be, privy or open, and thereto that will be ruled not after their own will and their own wit, but after the will and the counsel of their sovereigns, what so they be, religious or seculars, such a liking or a grumbling fastened in the fleshly heart is but venial sin. The cause of this is the grounding and the rooting of your intent in God, made in the beginning of your living in that state that ye stand in, by the witness and the counsel of some discreet father.
But if it so be, that this liking or grumbling fastened in thy fleshly heart p. 109 be suffered so long to abide unreproved, that then at the last it is fastened to the ghostly heart, that is to say the will, with a full consent: then, it is deadly sin. And this befalleth when thou or any of them that I speak of wilfully draw upon thee the remembrance of any man or woman living in this life, or of any bodily or worldly thing other: insomuch, that if it be a thing the which grieveth or hath grieved thee before, there riseth in thee an angry passion and an appetite of vengeance, the which is called Wrath. Or else a fell disdain and a manner of loathsomeness of their person, with despiteful and condemning thoughts, the which is called Envy. Or else a weariness and an unlistiness of any good occupation bodily or ghostly, the which is called Sloth.
And if it be a thing that pleaseth thee, or hath pleased thee before, there riseth in thee a passing delight for to think on that thing what so it be. Insomuch, p. 110 that thou restest thee in that thought, and finally fastenest thine heart and thy will thereto, and feedest thy fleshly heart therewith: so that thee think for the time that thou covetest none other wealth, but to live ever in such a peace and rest with that thing that thou thinkest upon. If this thought that thou thus drawest upon thee, or else receivest when it is put unto thee, and that thou restest thee thus in with delight, be worthiness of nature or of knowing, of grace or of degree, of favour or of fairhead, then it is Pride. And if it be any manner of worldly good, riches or chattels, or what that man may have or be lord of, then it is Covetyse. If it be dainty meats and drinks, or any manner of delights that man may taste, then it is Gluttony. And if it be love or plesaunce, or any manner of fleshly dalliance, glosing or flattering of any man or woman living in this life, or of thyself either: then it is Lechery. p. 111