Cardinal Manning states that mortal sins separate the soul from God, Who is the life of the soul, whereas venial sins “may be found in souls that are united with God, and are in the grace of God, and in the love of God, and in a state of habitual obedience.”
“The sins which may be found even in holy men are sins of infirmity committed through weakness; or sins of surprise committed by sudden or strong temptation; or sins of impetuosity, where passion carries a man for a moment beyond self-control; or sins of indeliberation, that is, done in haste, before as yet conscience and the reason have had time to deliberate and weigh what they are about; or lastly, they may be sins committed with some degree of deliberation.”
Even six of the capital sins—anger, pride, gluttony, avarice, envy, and sloth—”are susceptible of degrees and shades and distinctions,” and may be committed “through infirmity, through surprise, through impetuosity, and without deliberation, and even with some degree of deliberation, without being mortal.”
“We are labourers out in the field, and the soils and stains of our toil will cleave to us. We are wayfarers in the road, and the dust will settle upon us even when we do not know it. We cannot go out of the world and the world’s evil.”
“Even the saints of God, through infirmity, and through temptation, have offended against God, and yet they have not broken their friendship, nor separated their souls from Him.”
“We have got, then, what I may call a definition of venial sin. It is a transgression of the law of God; a thought, word, or deed at variance with the will of God, through infirmity, and without deliberate malice. This will suffice to distinguish the sin which is not unto death from that which I described last time, where, with eyes open and willing consent, a sinner breaks the law of God in the face of God.”
Quotations from Henry Edward Manning, Sin and Its Consequences, 2d ed. (London: Burns and Oates, 1874).