Thomas Aquinas, Summa Theologiae

Objection 1: It would seem that heavenly bodies impose necessity on things subject to their action. For given a sufficient cause, the effect follows of necessity. But heavenly bodies are a sufficient cause of their effects. Since, therefore, heavenly bodies, with their movements and dispositions, are necessary beings; it seems that their effects follow of necessity.

Objection 2: Further, an agent's effect results of necessity in matter, when the power of the agent is such that it can subject the matter to itself entirely. But the entire matter of inferior bodies is subject to the power of heavenly bodies, since this is a higher power than theirs. Therefore the effect of the heavenly bodies is of necessity received in corporeal matter.

Objection 3: Further, if the effect of the heavenly body does not follow of necessity, this is due to some hindering cause. But any corporeal cause, that might possibly hinder the effect of a heavenly body, must of necessity be reducible to some heavenly principle: since the heavenly bodies are the causes of all that takes place here below. Therefore, since also that heavenly principle is necessary, it follows that the effect of the heavenly body is necessarily hindered. Consequently it would follow that all that takes place here below happens of necessity.

On the contrary, The Philosopher says (De Somn. et Vigil. ): "It is not incongruous that many of the signs observed in bodies, of occurrences in the heavens, such as rain and wind, should not be fulfilled." Therefore not all the effects of heavenly bodies take place of necessity.

I answer that, This question is partly solved by what was said above (Article 4); and in part presents some difficulty. For it was shown that although the action of heavenly bodies produces certain inclinations in corporeal nature, the will nevertheless does not of necessity follow these inclinations. Therefore there is nothing to prevent the effect of heavenly bodies being hindered by the action of the will, not only in man himself, but also in other things to which human action extends.

But in natural things there is no such principle, endowed with freedom to follow or not to follow the impressions produced by heavenly agents. Wherefore it seems that in such things at least, everything happens of necessity; according to the reasoning of some of the ancients who supposing that everything that is, has a cause; and that, given the cause, the effect follows of necessity; concluded that all things happen of necessity. This opinion is refuted by Aristotle (Metaph. vi, Did. v, 3) as to this double supposition.

For in the first place it is not true that, given any cause whatever, the effect must follow of necessity. For some causes are so ordered to their effects, as to produce them, not of necessity, but in the majority of cases, and in the minority to fail in producing them. But that such cases do fail in the minority of cases is due to some hindering cause; consequently the above-mentioned difficulty seems not to be avoided, since the cause in question is hindered of necessity.

Therefore we must say, in the second place, that everything that is a being "per se," has a cause; but what is accidentally, has not a cause, because it is not truly a being, since it is not truly one. For (that a thing is) "white" has a cause, likewise (that a man is) "musical" has not a cause, but (that a being is) "white-musical" has not a cause, because it is not truly a being, nor truly one. Now it is manifest that a cause which hinders the action of a cause so ordered to its effect as to produce it in the majority of cases, clashes sometimes with this cause by accident: and the clashing of these two causes, inasmuch as it is accidental, has no cause. Consequently what results from this clashing of causes is not to be reduced to a further pre-existing cause, from which it follows of necessity. For instance, that some terrestrial body take fire in the higher regions of the air and fall to the earth, is caused by some heavenly power: again, that there be on the surface of the earth some combustible matter, is reducible to some heavenly principle. But that the burning body should alight on this matter and set fire to it, is not caused by a heavenly body, but is accidental. Consequently not all the effects of heavenly bodies result of necessity.

Reply to Objection 1: The heavenly bodies are causes of effects that take place here below, through the means of particular inferior causes, which can fail in their effects in the minority of cases.

Reply to Objection 2: The power of a heavenly body is not infinite. Wherefore it requires a determinate disposition in matter, both as to local distance and as to other conditions, in order to produce its effect. Therefore as local distance hinders the effect of a heavenly body (for the sun has not the same effect in heat in Dacia as in Ethiopia); so the grossness of matter, its low or high temperature or other such disposition, can hinder the effect of a heavenly body.

Reply to Objection 3: Although the cause that hinders the effect of another cause can be reduced to a heavenly body as its cause; nevertheless the clashing of two causes, being accidental, is not reduced to the causality of a heavenly body, as stated above.

Articulus 6

Argumentum 1

Ad sextum sic proceditur. Videtur quod corpora caelestia imponant necessitatem iis quae eorum actioni subduntur. Causa enim sufficienti posita, necesse est effectum poni. Sed corpora caelestia sunt sufficiens causa suorum effectuum. Cum igitur corpora caelestia, cum suis motibus et dispositionibus, ponantur sicut ex necessitate entia; videtur quod effectus eorum ex necessitate consequantur.

Argumentum 2

Praeterea, effectus agentis ex necessitate sequitur in materia, quando virtus agentis tanta fuerit quod possit sibi subiicere totaliter materiam. Sed tota materia inferiorum corporum subiicitur virtuti caelestium corporum, tanquam excellentiori. Ergo ex necessitate effectus caelestium corporum recipitur in materia corporali.

Argumentum 3

Praeterea, si effectus caelestis corporis non ex necessitate proveniat, hoc est propter aliquam causam impedientem. Sed quamlibet causam corpoream quae impedire posset effectum caelestis corporis, necesse est reduci in aliquod caeleste principium, cum caelestia corpora sint causa omnium quae hic fiunt. Ergo, cum et illud caeleste principium sit necessarium, sequitur quod necesse sit impediri effectum alterius corporis caelestis. Et sic omnia quae hic contingunt, ex necessitate eveniunt.

Sed Contra

Sed contra est quod philosophus dicit, in libro de somn. Et vigil., quod neque eorum quae in corporibus sunt signorum caelestium, velut aquarum et ventorum, inconveniens est multa non evenire.

Sic ergo non omnes effectus caelestium corporum ex necessitate eveniunt.

Corpus

Respondeo dicendum quod ista quaestio partim quidem absoluta est, secundum praemissa; partim autem difficultatem habet.

Ostensum enim est quod, quamvis ex impressione corporum caelestium fiant aliquae inclinationes in natura corporali, voluntas tamen non ex necessitate sequitur has inclinationes. Et ideo nihil prohibet per voluntariam actionem impediri effectum caelestium corporum, non solum in ipso homine, sed etiam in aliis rebus ad quas hominum operatio se extendit. Sed nullum tale principium invenitur in rebus naturalibus, quod habeat libertatem sequendi vel non sequendi impressiones caelestes. Unde videtur quod in talibus, ad minus, omnia ex necessitate proveniant, secundum antiquam quorundam rationem, qui, supponentes omne quod est causam habere, et quod, posita causa, ex necessitate ponitur effectus, concludebant, quod omnia ex necessitate contingant. Quam quidem opinionem repellit Aristoteles in VI metaphys., secundum duo quae ipsi supponunt. Primo enim, non est verum quod, posita quacumque causa, necesse sit effectum poni. Sunt enim quaedam causae quae ordinantur ad suos effectus non ex necessitate, sed ut in pluribus, quae quandoque deficiunt in minori parte. Sed quia huiusmodi causae non deficiunt in minori parte, nisi propter aliquam causam impedientem, videtur adhuc praedictum inconveniens non vitari, quia et ipsum impedimentum talis causae ex necessitate contingit. Et ideo, secundo, oportet dicere quod omne quod est per se, habet causam, quod autem est per accidens, non habet causam, quia non est vere ens, cum non sit vere unum. Album enim causam habet, similiter et musicum; sed album musicum non habet causam, quia non est vere ens, neque vere unum. Manifestum est autem quod causa impediens actionem alicuius causae ordinatae ad suum effectum ut in pluribus, concurrit ei interdum per accidens, unde talis concursus non habet causam, inquantum est per accidens. Et propter hoc, id quod ex tali concursu sequitur, non reducitur in aliquam causam praeexistentem, ex qua ex necessitate sequatur. Sicut quod aliquod corpus terrestre ignitum in superiori parte aeris generetur et deorsum cadat, habet causam aliquam virtutem caelestem, et similiter etiam quod in superficie terrae sit aliqua materia combustibilis, potest reduci in aliquod caeleste principium. Sed quod ignis cadens huic materiae occurrat et comburat eam, non habet causam aliquod caeleste corpus, sed est per accidens. Et sic patet quod non omnes effectus caelestium corporum sunt ex necessitate.

Ad 1

Ad primum ergo dicendum quod corpora caelestia sunt causa inferiorum effectuum mediantibus causis particularibus inferioribus, quae deficere possunt in minori parte.

Ad 2

Ad secundum dicendum quod virtus corporis caelestis non est infinita. Unde requirit determinatam dispositionem in materia ad inducendum suum effectum, et quantum ad distantiam loci, et quantum ad alias conditiones. Et ideo sicut distantia loci impedit effectum caelestis corporis (non enim sol eundem caloris effectum habet in dacia, quem habet in Aethiopia); ita et grossities materiae, vel frigiditas aut caliditas, aut alia huiusmodi dispositio, impedire potest effectum corporis caelestis.

Ad 3

Ad tertium dicendum quod licet causa impediens effectum alterius causae, reducatur in aliquod caeleste corpus sicut in causam; tamen concursus duarum causarum, cum sit per accidens, non reducitur in causam caelestem, ut dictum est.