The importance and pervasiveness of software systems makes software engineering a driver of the progress of humanity. Prof. Manny Lehman, with his constant, competent and passionate work, laid the foundation for an understanding of a key phenomenon that characterizes software engineering, namely the need for continuous evolution of software. With his idea that software, though an engineering creation, must be studied as a natural phenomenon and through his investigation of long-term implications of changes, Manny Lehman profoundly influenced the ways in which software is understood and created. Lehman's work has been ahead of his time in many respects. Together with Les Belady, he initiated the idea of in-the-field empirical studies, like their study of the evolution of IBM's OS 360, as they envisioned that such empirical work could lead to a better understanding of software engineering processes, which could in turn contribute to a better control of software cost and quality. His laws of software evolution, the uncertainty principle, and his view of the software process as a feedback system served as a foundation stone of many PhD thesis developed over the years in software maintenance and process improvement, thus making our community particularly indebted to his contributions.