If I Were King of the Forest…! — The Grammar, Meaning, and Logic of Conditional Statements

Abstract

This article provides a basic overview of the grammar of conditionals, the role of conditionality in predicate logic, and the difference between conditionality and causality. Medical writers must achieve mastery of these concepts, which are important not just for clear writing but for rational thinking. English speakers use conditionals for many different purposes, such as describing facts, habits, and rules (zero-order conditionals); describing the future consequences of realistic, possible, or likely events (first-order conditionals); expressing the likely consequence of some uncertain or impossible event (second-order conditionals); or talking about how things could have turned out differently if some condition had been met in the past (third-order conditionals). Conditionals also allow one to ask questions about the consequences of an event or to express the conditions under which a command should be followed. Conditional constructions are also sometimes used in expressions that don’t really express conditions (relevance conditionals). The grammatical differences between these expressions are subtle, involving the tense and mood of the verbs. Conditionals allow you to talk about how the truth-values of different propositions are interrelated. Thus, once you master the grammar of conditionals, you can begin to learn the rules and pitfalls of deductive and inductive reasoning. In science, such reasoning is often the first step toward proving causality. The existence of a tight correlation between two phenomena does not prove that one causes the other, but the lack of a correlation suggests that a causal relationship is unlikely.