Philosophy progresses in two ways. First, philosophical work mirrors the concerns of its historical time. For example, in the seventeenth century, when modern nations were forming, philosophers like John Locke (1632–1704) and Thomas Hobbes (1588–1679) wrote about the origins of modern, democratic government. In the twentieth century, philosophers have applied ethics to new choices made possible by modern medicine. The second form of progress in philosophy consists of the growth of philosophical thought over time. This progression of philosophy is largely a conversation among philosophers, who in one way or another are in dialogue with their historical predecessors, as well as their peers.