Philo the Dialectician

Little is known about the life of Philo. He was a disciple of Diodorus Cronus, and was a friend of Zeno, the founder of Stoicism. Diogenes Laërtius states that Zeno "used to dispute very carefully with Philo the logician and study along with him—hence Zeno, who was the junior, had as great an admiration for Philo as his master Diodorus."Diogenes Laërtius, vii. 16

Jerome refers to Philo as the teacher of Carneades, which is chronologically impossible.Jerome, Contra Jovinianum, i. 42 Diogenes Laërtius mentions a (presumably different) Philo who was a disciple of Pyrrho.Diogenes Laërtius, ix. 67, 69

One of Philo's works was called Menexenus in which he mentioned the five daughters of Diodorus who were all distinguished dialecticians.Clement of Alexandria, Stromata, iv. 19; cf. Jerome, Contra Jovinianum, i. 42 Two of Chrysippus' logical works were responses to books by Philo, one was directed at "Philo's Work on Meanings",Diogenes Laërtius, vii. 191 and the other at "Philo's Work on Moods".Diogenes Laërtius, vii. 194

Philo disputed with Diodorus respecting the idea of the possible and the criteria of the truth of conditional statements.

In regards to things possible, Diodorus maintained that possible was identical with necessary, i.e. that possible is "that which either is or will be true".{{cite SEP|url-id=logic-ancient|title=Ancient Logic|last=Bobzien|first=Susanne}} Philo instead defined possible as "that which is capable of being true by the proposition's own nature", thus a statement like "this piece of wood can burn" is possible, even if it spent its entire existence on the bottom of the ocean.Alexander of Aphrodisias, Nat. Qual. i. 14., In An. Pr. 183-4

Both Philo and Diodorus sought for criteria for the correct form of conditional propositions, and each of them did so in a manner corresponding to what he maintained respecting the idea of the possible. Philo regarded a conditional as true unless it has both a true antecedent and a false consequent. Precisely, let T₀ and T₁ be true statements, and let F₀ and F₁ be false statements; then, according to Philo, each of the following conditionals is a true statement, because it is not the case that the consequent is false while the antecedent is true (it is not the case that a false statement is asserted to follow from a true statement):

• If T₀, then T₁
• If F₀, then T₀
• If F₀, then F₁

The following conditional does not meet this requirement, and is therefore a false statement according to Philo:

• If T₀, then F₀''

Indeed, Sextus says "According to [Philo], there are three ways in which a conditional may be true, and one in which it may be false."Sextus Empiricus, Adv. Math. viii, Section 113 Philo's criterion of truth is what would now be called a truth-functional definition of "if ... then"; it is the definition used in modern logic.

In contrast, Diodorus allowed the validity of conditionals only when the antecedent clause could never lead to an untrue conclusion.Sextus Empiricus, Hypotyp. ii. 110, comp.Cicero, Academica, ii. 47, de Fato, 6. A century later, the Stoic philosopher Chrysippus attacked the assumptions of both Philo and Diodorus.

{{reflist}}

• {{cite SEP |url-id=dialectical-school |title=Dialectical School |last=Bobzien |first=Susanne}}
• [https://www.historyoflogic.com/biblio/master-argument-biblio.htm Selected Bibliography on the "Master Argument" in Diodorus Cronus and Philo the Dialectician] with a bibliography on the problem of future contingents

{{SmithDGRBM|article=Philon the Megarian or Dialectician |volume=III|page=312-313}}

{{Megarian philosophy}}

{{authority control}}

{{DEFAULTSORT:Philo The Dialectician}}

Category:Hellenistic-era philosophers

Category:4th-century BC Greek philosophers

Category:Megarian philosophers

Category:Ancient Greek logicians