Modus ponens is a fundamental rule of logic used in deductive reasoning. It states that if a conditional statement is true, and its antecedent (the "if" part) is also true, then the consequent (the "then" part) must also be true. For example, if we have the statement "If it rains, then the ground will be wet," and we know that it is indeed raining, we can conclude that the ground is wet. This logical form can be represented symbolically as: If P, then Q; P is true; therefore, Q is true. Modus ponens is widely used in mathematics, philosophy, and computer science to draw valid conclusions from given premises.