"That is to say that ideologies do not react passively, like weather vanes, to every shift in the political winds. On the contrary, ideologies try to shape and direct social change. The men and women who follow and promote political ideologies—and almost all of us do this in one way or another—try to make sense of the world, to understand society and politics and economics, in order either to change it for the better or to resist changes that they think will make it worse. But to act upon the world in this way, they must react to the changes that are always taking place, including the changes brought about by rival ideologies. Political ideologies, then, are dynamic. They do not stand still, because they cannot do what they want to do—shape the world—if they fail to adjust to changing conditions. This dynamic character of ideologies can be frustrating for anyone who wishes to understand exactlywhat a liberal or a conservative is, for it makes it impossible to define liberalism or conservatism or any other ideology with mathematical precision. But once we recognize that political ideologies are rooted in, change with, and themselves help to change historical circumstances, we are on the way to grasping what any particular ideology is about."