In the opening essay, Berlin notes that how people look at history and what they regard as the facts change over time and reflect specific periods. During the nineteenth century, there was a belief in progress and in rational solutions to the problems affecting human beings and society. That belief disintegrated in the twentieth century, giving rise to what Berlin calls an intellectual barrier between the two centuries and their view of the world and history.

In the twentieth century, people came to understand and stress the importance of the unconscious and irrational forces in human beings, and many came to believe that the answer to most problems is to remove the problem rather than solve it through rational thought and argument. For example, the problems associated with human liberty (such as dissidents, extremist political groups, or demonstrations) can be removed by eliminating the desire for liberty among the people. This was a solution shared equally by Nazi Germany and the Soviet Union when these governments denounced “bourgeois liberty” as hollow and useless.

Such an approach would create a perversely “ideal society” in which disturbing questions simply would not be raised because they could not even be conceived. This is the vision of George Orwell in Nineteen Eighty-Four (1949) and, slightly altered, that of Aldous Huxley in Brave New World (1932). Such a world can be achieved, Berlin argues, when there is a growing desire among people to accept security at the price of personal liberty. To avoid this fate, it is necessary to have less faith in systems and more trust in human intelligence operating in a condition of maximum freedom.