Tractatus De Signis

Description

PDF is 2nd edition (2013) reprinted and (partially) re-typeset by St. Augustine Press

Excerpt of John of St. Thomas's Ars Logica (Reiser ed.)

Euclid's definition of ratio in Element. (l. 5.) defins. as a "similitudo duarum proportionum " is mentioned in the context of "whether mind-independent relations themselves, precisely as such, are able to found other relations." Scotus thought so (cf. Deely's Four Ages of Understanding pp. 376-7, esp. where he summarizes, on the first full quoted ¶ on p. 377, Scotus's view: "unica requirit [Scotus] solum distinctionem inter res, quæ sunt extrema, non inter rationes fundandi. D. Thomas utrumque requirit "; cf. the Summa article "Whether there is equality in God?"); St. Thomas did not. cf. John of St. Thomas's Tractatus de Signis pp. 102 line 23ff.

Euclid:

3. A ratio (Λόγος) is a sort of relation in respect of size between two magnitudes of the same kind.6. Let magnitudes which have the same ratio be called proportional (ἁνάλογον).

facere cognoscere ⊃ repraesentare ⊃ significare

John of St. Thomas describes this hierarchy (ibid. p. 26): "facere cognoscere latius patet quam repraesentare, et repraesentare quam significare." Thus, that which represents (figure) has a larger extension than what merely explains / formally (or even instrumentally) signifies (explique). When Duhem says physical theories are not explanations, he by no means excludes their ability "facere [nos] cognoscere."

A sign that does not explain is merely an instrumental sign, but a formal sign (concept) "est formalis notitia, quae seipsa, non mediante alio, repraesentat" (Tractatus de Signis 27/13-14 (from his summulæ)).

Duhem used figurer ("to represent" or "to appear," correct?), not décrire :

le second a pour objet de constituer un modèle mécanique qui figure ou explique (pour un physicien anglais, les deux mots ont le même sens)⁷ les actions électriques et magnétiques.
[Figurer seems to be synonymous with "to save the appearances," and expliquer with "showing how phenomena result from their underlying causes."]

p. 117 (DjVu p. 131) n. 6: "Seu in classical Latin usage introduces an alternative condition or [vel?☺] a disjunction."

re: Galileo and Poinsot's editors' "suppressing the then-traditional fourfold division [which included astronomy] itself in favor of a tri-partite structure [sans astronomy]" and the alleged destruction of Poinsot's astronomy MSS to be printed in 1634: p. 403 (DjVu p. 417) n. 8 & p. 439 (DjVu p. 453) n. 55.