Computational Complexity: A Conceptual Perspective Oded Goldreich Complexity Theory is a central field of the theoretical foundations of computer science. It is concerned with the general study of the intrinsic complexity of computational tasks; that is, it addresses the question of what can be achieved within limited time (and/or with other limited natural computational resources). This book offers a conceptual perspective on Complexity Theory. It is intended to serve as an introduction for advanced undergraduate and graduate students, either as a textbook or for self-study. The book will also be useful to experts, since it provides expositions of the various sub-areas of Complexity Theory such as hardness amplification, pseudorandomness, and probabilistic proof systems. In each case, the author starts by posing the intuitive questions that are addressed by the sub-area and then discusses the choice made in the actual formulation of these questions, the approaches that lead to the answers, and the ideas that are embedded in these answers. Oded Goldreich is a Professor of Computer Science at the Weizmann Institute of Science and an Incumbent of the Meyer W. Weisgal Professorial Chair. He is an editor for the SIAM Journal of Computing, the Journal of Cryptology, and Computational Complexity and previously authored the books Modern Cryptography, Probabilistic Proofs and Pseudorandomness and the two-volume work Foundations of Cryptography