Diogenes Laërtius · fl. 3rd century CE
Lives of Eminent Philosophers 7.73 — Diogenes Laërtius on the Stoics
Translation by R. D. Hicks (1925)
Diogenes Laërtius, Lives of Eminent Philosophers 7.73
Reported speech · Diogenes Laërtius on the Stoics
Opposite in character to the foregoing is a proposition which declares what is less the fact, as e.g. “It is less or not so much night as day.” Further, among propositions there are some which in respect of truth and falsehood stand opposed to one another, of which the one is the negative of the other, as e.g. the propositions “It is day” and “It is not day.” A hypothetical proposition is therefore true, if the contradictory of its conclusion is incompatible with its premiss, e.g. “If it is day, it is light.” This is true. For the statement “It is not light,” contradicting the conclusion, is incompatible with the premiss “It is day.” On the other hand, a hypothetical proposition is false, if the contradictory of its conclusion does not conflict with the premiss, e.g. “If it is day, Dion is walking.” For the statement “Dion is not walking” does not conflict with the premiss “It is day.”
Cite this passage
Diogenes Laërtius, Lives of Eminent Philosophers 7.73 (on the Stoics), tr. R. D. Hicks (1925)
https://whatwouldstoicsdo.com/passage/lives-of-the-stoics/7.73
Diogenes Laërtius, Lives of Eminent Philosophers, Book VII, tr. R. D. Hicks (Loeb, 1925). Text: Perseus Digital Library (CC BY-SA 4.0). Sources and licences
In plain English
AI-written notesExplains opposed statements and when an if-then statement counts as true: when denying its conclusion would clash with its starting claim. Uses simple examples about day, light and Dion walking. Logic terminology.
Older wording
- “hypothetical proposition”
- — an if-then statement
- “contradictory”
- — the direct opposite of a statement
- “premiss”
- — the statement an argument starts from
Themes and situations
- Judgements and impressions
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