St. Thomas: Logic is Not a Science

St. Thomas: Logic is Not a Science

It is a rather common position among Thomistic scholars to consider logic as a science.  And St. Thomas in fact often calls it scientia rationalis in several texts.  However, I would argue that this is only an analogical and less strict use of the term, and that St. Thomas does not consider logic to be strictly speaking a science.  

In his Commentary on Boethius on the Trinity, q. 5, a. 1, ad 2, he argues that there are three genera of speculative sciences---natural science, mathematics, and metaphysics---and in the process clearly argues that logic is not a science, but rather "an instrument of science" (instrumentum scientiae).

Articulus 1

ARTICLE ONE Is Speculative Science Appropriately Divided into these Three Parts: Natural, Mathematical, and Divine?

Pars 3 q. 5 a. 1 arg. 1
Ad primum sic proceditur. Videtur quod speculativa inconvenienter in has partes dividatur...	We proceed as follows to the first article: It seems that speculative science is not appropriately divided into these three parts...

Pars 3 q. 5 a. 1 arg. 2
Praeterea, Augustinus dicit in VIII de civitate Dei quod rationalis philosophia, quae est logica, sub contemplativa philosophia vel speculativa continetur. Cum ergo de ea mentionem non faciat, videtur quod divisio sit insufficiens.	2. Again, Augustine says that rational philosophy, or logic, is included under contemplative or speculative philosophy. Consequently, since no mention is made of it, it seems the division is inadequate.

Pars 3 q. 5 a. 1 ad 2

Ad secundum dicendum quod scientiae speculativae, ut patet in principio metaphysicae, sunt de illis quorum cognitio quaeritur propter se ipsa. Res autem, de quibus est logica, non quaeruntur ad cognoscendum propter se ipsas, sed ut adminiculum quoddam ad alias scientias. Et ideo logica non continetur sub speculativa philosophia quasi principalis pars, sed sicut quiddam reductum ad philosophiam speculativam, prout ministrat speculationi sua instrumenta, scilicet syllogismos et diffinitiones et alia huiusmodi, quibus in scientiis speculativis indigemus. Unde secundum Boethium in commento super Porphyrium non tam est scientia quam scientiae instrumentum.

Reply to 2. As is evident in the beginning of the Metaphysics, the speculative sciences concern things the knowledge of which is sought for their own sake. However, we do not seek to know the things studied by logic for themselves, but as a help to the other sciences. So logic is not included under speculative philosophy as a principal part but as something brought under speculative philosophy as furnishing speculative thought with its instruments, namely, syllogisms, definitions, and the like, which we need in the speculative sciences. Thus, according to Boethius, logic is not so much a science as the instrument of science.

Text Source: The Logic Museum.