Entailment
A proposition P entails Q when P cannot be true while Q is false. This is a test of interpretations, not a judgment about whether a historical report is factually correct. For an ancient passage, first settle ambiguity in the underlying sentence. Then state P and the proposed Q separately and ask whether any coherent reading permits P to be true and Q false.
In a historical text, the statement that an event happened is evidence that a writer made that statement, not independent proof that the event happened. Keep the semantics of the sentence separate from the historian’s evaluation of the claim.
Presupposition
A presupposition is backgrounded content treated as already established by a construction. The cited textbook analyzes stop as a change-of-state trigger: its example presupposes an earlier state, and that background content tends to remain when the assertion is negated. This projection test is useful but not mechanical, since discourse can challenge or accommodate a presupposition and languages package background information differently.
For a source text, identify the lexical or grammatical trigger before attributing a presupposition to its author. A modern translator’s connective, change-of-state verb or definite article may introduce background meaning not explicitly encoded in the source. Check whether the original has a corresponding element and what its attested uses show.
Implicature
An implicature is an inference conveyed in context without being part of what the sentence straightforwardly entails. A test is whether the inference can be denied without contradicting the assertion. Its plausibility can change when the speaker, addressee or shared expectations change. With an ancient document, establish those contextual factors from the surviving evidence before proposing a specific implicature. Do not confidently infer irony, politeness or omission when the interactional setting is largely lost.
A useful notebook has three lines: asserted or at-issue content; presupposed background with its trigger; plausible contextual inference with its evidential basis. Mark alternative analyses.
Modern-language examples on this page clarify a linguistic pattern. They do not establish unattested sounds or forms for an ancient language. Follow the cited sources below and keep editorial readings separate from the surviving trace.