Chapter — Billuart, Summa Summae · from Schola Thomistica
On Moderate Probabilism
as the sun illuminates by its rays things previously obscure to us, which become visible when those rays are reflected back to us. And for this reason principles of this kind are rightly called reflex. In this therefore consists the efficacy of these very principles, that, since the existence of some law can be affirmed only probably, and by that very fact the obligation of observing such a law remains doubtful, from the aforesaid principles it is pronounced whether one acting against a doubtful law can act licitly, or whether he is bound to observe it.
sicut sol radiis suis illuminat res quae antea nobis obscura, his radiis ad nos repercussis visibiles fiunt. Et propter hoc hujusmodi principia recte vocantur reflexa. In hoc ergo consistit efficacia horumce principiorum, quod, cum existentia alicujus legis nonnisi probabiliter affirmari potest, et eo ipso obligatio talem legem observandi dubia remanet, ex principiis praedictis pronuntiatur an agens contra legem dubiam licite agere possit, an vero teneatur eam observare.
That 5° reflex principles are necessary for solving the practical doubts here treated of is demonstrated from the very fact itself. For whatever opinion prevail in the present matter, immediately some reflex principle intervenes. Tutiorists, as well as probabilists, are compelled to concede that a doubtful law as such does not oblige, that is, in reason of the doubt itself, because doubt is a negative thing, from which nothing positive, such as obligation, can arise. On either side therefore recourse is had to some external principle, for determining what is practically to be decided. Tutiorists, affirming obligation in every doubt, lean upon this reflex principle : « In doubt the safer part must be followed. » Probabilists, who deny obligation, since the opinion opposed to the law is truly and solidly probable, place among the reflex principles they allege this principal one : « A doubtful law does not oblige. » Therefore in the present question some reflex principle necessarily intervenes.]
5° Principia reflexa necessaria esse ad solvenda dubia practica de quibus hic agitur, ex facto ipso demonstratur. Etenim, quaevis opinio in praesenti materia praevaleat, statim aliquod principium reflexum intercedit. Tutioristae, sicut et probabilistae, concedere coguntur legem dubiam ut talem non obligare, id est ratione ipsius dubii, quia dubium est quid negativum, ex quo oriri nequit aliquid positivum, qualis est obligatio. Ex utraque parte ergo recurritur ad aliquod principium extrinsecum, ad statuendum quid practice sit determinandum. Tutioristae, in quovis dubio obligationem affirmantes, hoc principio reflexo innituntur : « In dubio pars tutior est sequenda. » Probabilistae, qui negant obligationem, cum sententia legi opposita est vere et solide probabilis, inter principia reflexa quae allegant hoc precipuum ponunt : « Lex dubia non obligat. » Ergo in praesenti quaestione aliquod principium reflexum necessario intervenit.]
Within this chapter
- On the nature of probability
- What systems have arisen concerning probability in practical matters?
- Whether it is lawful to follow an opinion truly and solidly probable favoring liberty, leaving a safer one equally probable, or even more probable, where only the liceity of the action is at stake?
- On the use of probability, and the special rules by which conscience is practically formed in doubts
- Whether it is lawful to follow a probable, or even more probable, opinion, leaving the safer, when there is a certain obligation of attaining a determinate end?
- On Compensative Probabilism