A form of logical reasoning based on conditional statements or conditional propositions having the form If p, then q, in which p is the antecedent and q is the consequent. An example is If this substance is glass, then a diamond will scratch it. The conditional statement is logically equivalent to Not-(p and not-q), and it is true, by definition, if and only if p and q are both true or p is false (whether q is true or false). A subjunctive conditional is a conditional statement or proposition (1) in which the antecedent and consequent are both hypothetical or contingent: If the polar ice cap were to melt, then many people would drown. A counterfactual conditional is a subjunctive conditional in which the antecedent is not merely hypothetical but false: If she had pulled the trigger, then I would have been killed; and in logic it is necessarily true because its antecedent is false. See also affirming the antecedent, affirming the consequent, biconditional, denying the antecedent, denying the consequent, simulation heuristic.