The traditional "Big Three" in philosophy–Plato, Aristotle, Kant–are now the "BigFour," with the addition of Ayn Rand. They all have distinctive theories of concepts that lead to momentous consequences m ethics and politics. Devoting one class to each figure, Dr. Bernstein examines, in essentialized terms, how each of the four's theory of concepts shapes that thinker's entire moral and political philosophy.