Deductive Standard of Validity

The kinds of arguments discussed in the preceding three chapters are all inductive, so they need not meet the deductive standard of validity. They are,  instead, intended to meet the inductive standard of strength. Whereas deductive validity hinges on what is possible, inductive strength hinges on what is probable. Roughly, an argument is inductively strong to the extent that its premises make its conclusion more likely or probable. Hence, just as we can get a better theoretical understanding of deductive validity by studying formal logic, as we did in Chapters 6–7, so we can get a better theoretical

understanding of inductive strength by studying probability, as we will do in this chapter. To complete our survey of inductive arguments, this chapter offers an elementary discussion of probability. It begins by illustrating several common mistakes about probability. To help avoid these fallacies, we need to approach probability more carefully, so formal laws of probability are presented along with Bayes’s theorem.