A mode of inference according to which arbitrary conjuncts may be conjoined to the antecedent of a conditional without loss of truth. More formally, in deductive systems with a conditional connective $\to$ and a conjunction $\wedge$, this may be represented by the validity of the inference

The legitimacy of this inference is resisted by various non-classical logics. Possible counterexamples to the validity of antecedent strengthening have been suggested; in, e.g., the field of conditional logic, some have noted that the truth of a natural language conditional such as

• • If Penelope goes to the beach, then she will swim.

does not appear to entail the truth of

• • If Penelope goes to the beach and the ocean is teeming with sharks, then she will swim.