This anthology contains 31 significant papers in mathematical logic, mostly published in the second half of the twentieth century. Sacks, selecting on the basis of brevity as well as results, includes the work of Godel ("Consistency-Proof for the Generalized Continuum- Hypothesis"), Kleene ("Recursive Functionals and Quantifiers of Finite Types"), Tarski ("A Decision Method for Elementary Algebra and Geometry"), Robinson ("Non-Standard Analysis"), Kriesel ("Model- Theoretic Invariants"), Cohen (both parts of "The Independence of the Continuum Hypothesis"), Morley ("Categoricity in Power"), Shelah ("Stable Theories"), Hrushovski ("The Mordell-Lang Conjecture for Function Fields") and Woodin ("Supercompact Cardinals, Sets of Reals, and Weakly Homogeneous Trees").