Lorenzo Peña

The concept of every real thing from all eternity contains the unavoidability of its existence before the divine decision. Thus every complete concept of a real thing contains the property of being such that the thing will exist if a created universe exists. Then a thing's existence cannot be external to its concept. There is bound to be more in the concept of something that exists than in that of "something" that does not-since existence is explained through the quidditative property of being an essence that constitutes an integral part of the most perfect series of things. Such an essential, quidditative perfection explains the divine decision, and hence existence. Therefore, existence can be deduced from that essential perfection. The essence-as-such, the mere possible, contains something from which existence follows. What Leibniz never manages to explain is what distinguishes existence from the quidditative perfection it unavoidably stems from. (edited)

It is widely known that Plato seems to be committed in a number of dialogues to the view that all perfections are “united” — whether such unity is construed as identity, which doesn’t lack textual evidence, or, more probably, as some kind of mutual “supervenience”. (See for instance Laches 199e3-4, Alcib. I 114d-116d, Protag. 329c-333d & 349a-c. Whatever the solution to those interpretive problems is, what anyway can be ascertained is that, when writing the Statesman, our philosopher is keen on maintaining that not only is it not the case that all perfections are identical, but, moreover, some perfections do in fact clash with others, which means that a thing can possess one of them only to the extent it lacks the opposite perfection. However, as we’re going to see straight away, the Statesman’s main purpose and thrust is likely to be that of emphasizing the necessity of some unity among opposite qualities. The significance of such a contention can be set off against what will become the Aristotelian (and in effect the commonly received) view on the topic. In the Statesman Plato recognizes that in each case there is some desirable mean between the extremes, but where it lies changes according to circumstances. Trying to secure that convenient mean doesn’t debar us from loking upon the extremes under consideration as virtues or perfections themselves. Thus, when the Statesman is drawing towards its conclusion, the Foreigner abruptly brings up the issue of υπερβολην και την ελλειψιν (283c3-4), and thereby that of the art of measuring (η µετρητικη). Immediately the problem arises of the relations between the opposite extremes. In Theaet. 152d, 157a, 160b-c, it appears that Plato distinguishes relative from non-relative properties or determinations in the same way as he does between empirical, earthly, changeable things and the Forms. Yet in his later dialogues Plato is clearly committed to holding the view that the Forms themselves enter a number of relations, and even that some Forms partake of others. Since very early onwards he seems to have been concerned about some reciprocal relativity of opposite qualities (there are many places where such relativity is stressed, as Charm. 168b5-169a5, Phaed..

Da Costa's paraconsistent systems of the series Cm (for finite m) (see [C1], [C2], and esp. [C3], pp. 237ff.) share important features with transitive logic, TL (which has been gone into in [P1] and [P2]), namely, they all coincide in that: (c1) they possess a strong negation, `¬', a conditional, `⊃', a conjunction, `∧', and a disjunction, `∨', with respect to which they are conservative extensions of CL or Classical Logic; (c2) they possess a non strong negation, `N' (notations are different for systems C) which does not possess all properties of classical negation, but for which the following schemata are theorematic (I use the letters `p', `q', etc as schematic letters; my notational conventions are basically Church's: associativity leftwards; a dot stands for..