In recent years, Robert Heilbroner planned a book to develop the ideas presented in the new and final chapter he added to the seventh edition of his landmark book, The Worldly Philosophers, now fifty years old. As his health deteriorated and he was forced to abandon the project, he proposed an alternative project in which a group of thoughtful (although not like-minded) economists would instead respond to his arguments. The result is this special issue of Social Research.Sixteen world-class economists and philosophers have contributed to this festschrift issue, extending Heilbroners discussion of the great dynamics of capitalism. Some of their essays focus on the social embeddedness of markets in the 21st century. Others examine the ethical and political dimensions of contemporary economics and especially its conception of rationality. A third group of essays provides an assessment and critique of worldly philosophy as an economic method. Together, these far-reaching essays explore the current state of economic thought and the prospects for 21st century capitalism.