Deductive Inference >>> Inferences

Aquinas’s version of the Design Argument is deductively valid—the conclusion can’t be false if the premises are true. But the conclusion in a deductively valid argument cannot go beyond what is already contained in the premises.

Non-Deductive Inference >>> Inferences

William Paley’s version of the Design Argument is not a deductive argument—only an inference to the best explanation. Consequently, Paley's argument is not deductively valid.

Paley’s watchmaker argument can be considered an abductive argument (a type of non-deductive argument).