1 Objection 1: It would seem that men are not guarded by the angels. For guardians are deputed to some because they either know not how, or are not able, to guard themselves, as children and the sick. But man is able to guard himself by his free-will; and knows how by his natural knowledge of natural law. Therefore man is not guarded by an angel.
1 Ad primum sic proceditur. Videtur quod homines non custodiantur ab Angelis. Custodes enim deputantur aliquibus vel quia nesciunt, vel quia non possunt custodire seipsos; sicut pueris et infirmis. Sed homo potest custodire seipsum per liberum arbitrium; et scit, per naturalem cognitionem legis naturalis. Ergo homo non custoditur ab Angelo.
2 Objection 2: Further, a strong guard makes a weaker one superfluous. But men are guarded by God, according to Ps. 120, 4: He shall neither slumber nor sleep, that keepeth Israel. Therefore man does not need to be guarded by an angel.
2 Praeterea, ubi adest fortior custodia, infirmior superfluere videtur. Sed homines custodiuntur a Deo; secundum illud Psalmi CXX, non dormitabit neque dormiet qui custodit Israel. Ergo non est necessarium quod homo custodiatur ab Angelo.
3 Objection 3: Further, the loss of the guarded redounds to the negligence of the guardian; hence it was said to a certain one: Keep this man; and if he shall slip away, thy life shall be for his life 3 Kgs. 20, 39). Now many perish daily through falling into sin; whom the angels could help by visible appearance, or by miracles, or in some such-like way. The angels would therefore be negligent if men are given to their guardianship. But that is clearly false. Therefore the angels are not the guardians of men.
3 Praeterea, perditio custoditi redundat in negligentiam custodis, unde dicitur cuidam, III Reg. XX, custodi virum istum, qui si lapsus fuerit, erit anima tua pro anima eius. Sed multi homines quotidie pereunt, in peccatum cadentes, quibus Angeli subvenire possent vel visibiliter apparendo, vel miracula faciendo, vel aliquo simili modo. Essent ergo negligentes Angeli, si eorum custodiae homines essent commissi, quod patet esse falsum. Non igitur Angeli sunt hominum custodes.
4 On the contrary, It is written Ps. 90, 11): He hath given His angels charge over thee, to keep thee in all thy ways.
4 Sed contra est quod dicitur in Psalmo, Angelis suis mandavit de te, ut custodiant te in omnibus viis tuis.
5 I answer that, According to the plan of Divine Providence, we find that in all things the movable and variable are moved and regulated by the immovable and invariable; as all corporeal things by immovable spiritual substances, and the inferior bodies by the superior which are invariable in substance. We ourselves also are regulated as regards conclusions, about which we may have various opinions, by the principles which we hold in an invariable manner. It is moreover manifest that as regards things to be done human knowledge and affection can vary and fail from good in many ways; and so it was necessary that angels should be deputed for the guardianship of men, in order to regulate them and move them to good.
5 Respondeo dicendum quod, secundum rationem divinae providentiae, hoc in rebus omnibus invenitur, quod mobilia et variabilia per immobilia et invariabilia moventur et regulantur; sicut omnia corporalia per substantias spirituales immobiles, et corpora inferiora per corpora superiora, quae sunt invariabilia secundum substantiam. Sed et nos ipsi regulamur circa conclusiones in quibus possumus diversimode opinari, per principia quae invariabiliter tenemus. Manifestum est autem quod in rebus agendis cognitio et affectus hominis multipliciter variari et deficere possunt a bono. Et ideo necessarium fuit quod hominibus Angeli ad custodiam deputarentur, per quos regularentur et moverentur ad bonum.
6 Reply to Objection 1: By free-will man can avoid evil to a certain degree, but not in any sufficient degree; forasmuch as he is weak in affection towards good on account of the manifold passions of the soul. Likewise universal natural knowledge of the law, which by nature belongs to man, to a certain degree directs man to good, but not in a sufficient degree; because in the application of the universal principles of law to particular actions man happens to be deficient in many ways. Hence it is written Wis. 9, 14): The thoughts of mortal men are fearful, and our counsels uncertain. Thus man needs to be guarded by the angels.
6 Ad primum ergo dicendum quod per liberum arbitrium potest homo aliqualiter malum vitare, sed non sufficienter, quia infirmatur circa affectum boni, propter multiplices animae passiones. Similiter etiam universalis cognitio naturalis legis, quae homini naturaliter adest, aliqualiter dirigit hominem ad bonum, sed non sufficienter, quia in applicando universalia principia iuris ad particularia opera, contingit hominem multipliciter deficere. Unde dicitur Sap. IX, cogitationes mortalium timidae, et incertae providentiae nostrae. Et ideo necessaria fuit homini custodia Angelorum.
7 Reply to Objection 2: Two things are required for a good action; first, that the affection be inclined to good, which is effected in us by the habit of mortal virtue. Secondly, that reason should discover the proper methods to make perfect the good of virtue; this the Philosopher Ethic. vi) attributes to prudence. As regards the first, God guards man immediately by infusing into him grace and virtues; as regards the second, God guards man as his universal instructor, Whose precepts reach man by the medium of the angels, as above stated Question 111, Article 1).
7 Ad secundum dicendum quod ad bene operandum duo requiruntur. Primo quidem, quod affectus inclinetur ad bonum, quod quidem fit in nobis per habitum virtutis moralis. Secundo autem, quod ratio inveniat congruas vias ad perficiendum bonum virtutis, quod quidem philosophus attribuit prudentiae. Quantum ergo ad primum, Deus immediate custodit hominem, infundendo ei gratiam et virtutes. Quantum autem ad secundum, Deus custodit hominem sicut universalis instructor, cuius instructio ad hominem provenit mediantibus Angelis, ut supra habitum est.
8 Reply to Objection 3: As men depart from the natural instinct of good by reason of a sinful passion, so also do they depart from the instigation of the good angels, which takes place invisibly when they enlighten man that he may do what is right. Hence that men perish is not to be imputed to the negligence of the angels but to the malice of men. That they sometimes appear to men visibly outside the ordinary course of nature comes from a special grace of God, as likewise that miracles occur outside the order of nature.
8 Ad tertium dicendum quod, sicut homines a naturali instinctu boni discedunt propter passionem peccati; ita etiam discedunt ab instigatione bonorum Angelorum, quae fit invisibiliter per hoc quod homines illuminant ad bene agendum. Unde quod homines pereunt, non est imputandum negligentiae Angelorum, sed malitiae hominum. Quod autem aliquando, praeter legem communem, hominibus visibiliter apparent, ex speciali Dei gratia est, sicut etiam quod praeter ordinem naturae miracula fiunt.