Stefan Waner and Steven R. Costenoble of Hofstra University begin this online textbook by assigning students to prove the existence of God. This leads them to a concise discussion not of faith but of symbolic logic. This resource covers: statements and logical operators; logical equivalence, tautologies and contradictions; the conditional and biconditional; tautological implications and equivalences; rules of inference; and arguments and proofs. Each section is accompanied by exercises, with answers provided to odd-numbered exercises. And while the user might not be able to answer the original assignment after finishing Introduction to Logic, he or she will certainly have a more disciplined idea of how to think about it. Note that navigation is through the colored buttons adjacent to the chapter titles and exercises.