What will a definitive programming language look like? By definitive language I mean a programming language that gives good soat its level of abstraction, allowing computer science researchers to move on and work at higher levels. Given the evolution of computer as a field with a rising level of abstraction, it is my belief that a small set of definitive languages will eventually exist. But how can we learn something about this set, considering that many basic questions about languages have not yet been settled? In this paper, I give some tentative conclusions about one definitive language. I present four case studies of substantial research projects that tackle important problems in four quite different areas: fault-tolerant programming, secure distributed programming, network-transparent distributed programming, and teaching programming as a unified discipline. All four projects had to think about language design. In this paper, I summarize the reasons why each project designed the l...