In this paper, we present a logic for conditional strong historical necessity in branching time and apply it to analyze a nontheological version of Lavenham's argument for future determinism. Strong historical necessity is motivated from a linguistical perspective, and an example of it is ``If I had not gotten away, I must have been dead''. The approach of the logic is as follows. The agent accepts ontic rules concerning how the world evolves over time. She takes some rules as indefeasible, which determine acceptable timelines. When evaluating a sentence with conditional strong historical necessity, we introduce its antecedent as an indefeasible ontic rule and then check whether its consequent holds for all acceptable timelines. The argument is not sound by the logic.

翻译：本文提出了一种分支时间中条件强历史必然性的逻辑，并应用该逻辑分析了拉文汉姆未来决定论论证的一个非神学版本。强历史必然性从语言学视角获得动机，其一个例子是“若我未能逃脱，则我必定已死”。该逻辑的处理方法如下：主体接受关于世界如何随时间演化的本体规则，并将其中一些规则视为不可废止的，这些规则决定了可接受的时间线。在评估一个包含条件强历史必然性的语句时，我们将其前件作为一条不可废止的本体规则引入，然后检查其后件是否在所有可接受的时间线上成立。根据该逻辑，该论证并不健全。