Full Idea
From 'E will take place is true' it follows that E must take place. But 'must' here is logical not causal necessity. It is a considerable achievement of Carneades to have distinguished these two senses of necessity.
Gist of Idea
Carneades distinguished logical from causal necessity, when talking of future events
Source
comment on Carneades (fragments/reports [c.174 BCE]) by A.A. Long - Hellenistic Philosophy 3
Book Reference
Long,A.A.: 'Hellenistic Philosophy' [Duckworth 1986], p.103
A Reaction
Personally I am inclined to think 'necessity' is univocal, and does not have two senses. What Carneades has nicely done is distinguish the two different grounds for the necessities.
Related Idea
Idea 21388 The causes of future true events must exist now, so they will happen because of destiny [Chrysippus, by Cicero]