Thomas Aquinas, Summa Theologiae

Objection 1: It would seem that the devil is directly the cause of man's sinning. For sin consists directly in an act of the appetite. Now Augustine says (De Trin. iv, 12) that "the devil inspires his friends with evil desires"; and Bede, commenting on Acts 5:3, says that the devil "draws the mind to evil desires"; and Isidore says (De Summo Bono ii, 41; iii, 5) that the devil "fills men's hearts with secret lusts." Therefore the devil is directly the cause of sin.

Objection 2: Further, Jerome says (Contra Jovin. ii, 2) that "as God is the perfecter of good, so is the devil the perfecter of evil." But God is directly the cause of our good. Therefore the devil is directly the cause of our sins.

Objection 3: Further, the Philosopher says in a chapter of the Eudemein Ethics (vii, 18): "There must needs be some extrinsic principle of human counsel." Now human counsel is not only about good things but also about evil things. Therefore, as God moves man to take good counsel, and so is the cause of good, so the devil moves him to take evil counsel, and consequently is directly the cause of sin.

On the contrary, Augustine proves (De Lib. Arb. i, 11) that "nothing else than his own will makes man's mind the slave of his desire." Now man does not become a slave to his desires, except through sin. Therefore the cause of sin cannot be the devil, but man's own will alone.

I answer that, Sin is an action: so that a thing can be directly the cause of sin, in the same way as anyone is directly the cause of an action; and this can only happen by moving that action's proper principle to act. Now the proper principle of a sinful action is the will, since every sin is voluntary. Consequently nothing can be directly the cause of sin, except that which can move the will to act.

Now the will, as stated above (Question 9, Articles 3,4,6), can be moved by two things: first by its object, inasmuch as the apprehended appetible is said to move the appetite: secondly by that agent which moves the will inwardly to will, and this is no other than the will itself, or God, as was shown above (Question 9, Articles 3,4,6). Now God cannot be the cause of sin, as stated above (Question 79, Article 1). Therefore it follows that in this respect, a man's will alone is directly the cause of his sin.

As regards the object, a thing may be understood as moving the will in three ways. First, the object itself which is proposed to the will: thus we say that food arouses man's desire to eat. Secondly, he that proposes or offers this object. Thirdly, he that persuades the will that the object proposed has an aspect of good, because he also, in a fashion, offers the will its proper object, which is a real or apparent good of reason. Accordingly, in the first way the sensible things, which approach from without, move a man's will to sin. In the second and third ways, either the devil or a man may incite to sin, either by offering an object of appetite to the senses, or by persuading the reason. But in none of these three ways can anything be the direct cause of sin, because the will is not, of necessity, moved by any object except the last end, as stated above (Question 10, Articles 1,2). Consequently neither the thing offered from without, nor he that proposes it, nor he that persuades, is the sufficient cause of sin. Therefore it follows that the devil is a cause of sin, neither directly nor sufficiently, but only by persuasion, or by proposing the object of appetite.

Reply to Objection 1: All these, and other like authorities, if we meet with them, are to be understood as denoting that the devil induces man to affection for a sin, either by suggesting to him, or by offering him objects of appetite.

Reply to Objection 2: This comparison is true in so far as the devil is somewhat the cause of our sins, even as God is in a certain way the cause of our good actions, but does not extend to the mode of causation: for God causes good things in us by moving the will inwardly, whereas the devil cannot move us in this way.

Reply to Objection 3: God is the universal principle of all inward movements of man; but that the human will be determined to an evil counsel, is directly due to the human will, and to the devil as persuading or offering the object of appetite.

Articulus 1

Argumentum 1

Ad primum sic proceditur. Videtur quod diabolus sit homini directe causa peccandi.

Peccatum enim directe in affectu consistit.

Sed Augustinus dicit, IV de Trin., quod diabolus suae societati malignos affectus inspirat.

Et beda, super Act., dicit quod diabolus animam in affectum malitiae trahit.

Et Isidorus dicit, in libro de summo bono, quod diabolus corda hominum occultis cupiditatibus replet.

Ergo diabolus directe est causa peccati.

Argumentum 2

Praeterea, Hieronymus dicit quod sicut deus est perfector boni, ita diabolus est perfector mali.

Sed deus est directe causa bonorum nostrorum.

Ergo diabolus est directe causa peccatorum nostrorum.

Argumentum 3

Praeterea, philosophus probat, in quodam cap. Ethicae eudemicae, quod oportet esse quoddam principium extrinsecum humani consilii.

Consilium autem humanum non solum est de bonis, sed etiam de malis. Ergo sicut deus movet ad consilium bonum, et per hoc directe est causa boni; ita diabolus movet hominem ad consilium malum, et per hoc sequitur quod diabolus directe sit causa peccati.

Sed Contra

Sed contra est quod Augustinus probat, in I et III de Lib. Arb., quod nulla alia re fit mens hominis serva libidinis, nisi propria voluntate.

Sed homo non fit servus libidinis nisi per peccatum. Ergo causa peccati non potest esse diabolus, sed sola propria voluntas.

Corpus

Respondeo dicendum quod peccatum actus quidam est. Unde hoc modo potest esse aliquid directe causa peccati, per quem modum aliquis directe est causa alicuius actus. Quod quidem non contingit nisi per hoc quod proprium principium illius actus movet ad agendum. Proprium autem principium actus peccati est voluntas, quia omne peccatum est voluntarium.

Unde nihil potest directe esse causa peccati, nisi quod potest movere voluntatem ad agendum. Voluntas autem, sicut supra dictum est, a duobus moveri potest, uno modo, ab obiecto, sicut dicitur quod appetibile apprehensum movet appetitum; alio modo, ab eo quod interius inclinat voluntatem ad volendum. Hoc autem non est nisi vel ipsa voluntas, vel deus, ut supra ostensum est.

Deus autem non potest esse causa peccati, ut dictum est.

Relinquitur ergo quod ex hac parte sola voluntas hominis sit directe causa peccati eius.

Ex parte autem obiecti, potest intelligi quod aliquid moveat voluntatem tripliciter. Uno modo, ipsum obiectum propositum, sicut dicimus quod cibus excitat desiderium hominis ad comedendum. Alio modo, ille qui proponit vel offert huiusmodi obiectum. Tertio modo, ille qui persuadet obiectum propositum habere rationem boni, quia et hic aliqualiter proponit proprium obiectum voluntati, quod est rationis bonum verum vel apparens.

Primo igitur modo, res sensibiles exterius apparentes movent voluntatem hominis ad peccandum, secundo autem et tertio modo, vel diabolus, vel etiam homo, potest incitare ad peccandum, vel offerendo aliquid appetibile sensui, vel persuadendo rationi.

Sed nullo istorum trium modorum potest aliquid esse directa causa peccati, quia voluntas non ex necessitate movetur ab aliquo obiecto nisi ab ultimo fine, ut supra dictum est; unde non est sufficiens causa peccati neque res exterius oblata, neque ille qui eam proponit, neque ille qui persuadet.

Unde sequitur quod diabolus non sit causa peccati directe et sufficienter; sed solum per modum persuadentis, vel proponentis appetibile.

Ad 1

Ad primum ergo dicendum quod omnes illae auctoritates, et si quae similes inveniantur, sunt referendae ad hoc quod diabolus suggerendo, vel aliqua appetibilia proponendo, inducit in affectum peccati.

Ad 2

Ad secundum dicendum quod similitudo illa est attendenda quantum ad hoc, quod diabolus quodammodo est causa peccatorum nostrorum, sicut deus est aliquo modo causa bonorum nostrorum. Non tamen attenditur quantum ad modum causandi, nam deus causat bona interius movendo voluntatem, quod diabolo convenire non potest.

Ad 3

Ad tertium dicendum quod deus est universale principium omnis interioris motus humani, sed quod determinetur ad malum consilium voluntas humana, hoc directe quidem est ex voluntate humana; et a diabolo per modum persuadentis, vel appetibilia proponentis.