This study aims at exploring the various semantic effects of the French temporal conjunctionavant que(“before”). It shows howavant que, as a simple marker of anteriority, reacts to its linguistic context in such a way that new meanings emerge, which cannot be directly attributed to the conjunction.Viaa presuppositional analysis that takes into account factual as well as “counterfactual” or “suspensive” readings ofavant que, and through numerous attested examples, it reveals the mechanisms which are responsible for generating specific semantic effects. These effects are divided into three major categories, ranging frompreventing(avant que Pas “in order that not P” or “in such a way that not P”) toallowing(avant que Pas “in order that P”), or deliberating (avant que Pas “in order to decide if P”).