In this essay I propose to explore what we can and cannot learn about the way economies evolve over time. The focus of the essay is on the dynamics of change--political, social, and of course economic; and therefore the key word is time. In section I I outline the process of economic change as I understand it; in section II I specify the questions we must answer in order to understand that process; in the final section I tentatively identify which of those questions I believe are amenable to being answered with sufficient research and which I believe to be beyond our ability to answer. I need hardly add that my conclusions are highly speculative.