which he saw as the perfect state of the Golden Age. While Plato deviated from the tenets of historicism by believing in an ideal state that does not change, he shared with Heraclitus a tendency to shrink back from the last consequences of historicism. This chapter introduces Popper's distinction between the social engineer and the historicist, of which he favors the former. The social engineer believes that humans can control history to achieve their goals, and sees politics as a tool to build and modify social institutions; he evaluates institutions based on their design, efficiency, and other practical factors. (Popper identifies two types of social engineering: piecemeal and utopian, which he further discusses in chapter nine.) In contrast, the historicist is interested in understanding the past, present, and future significance of institutions. They evaluate institutions based on their historical role, such as if they are divinely willed or serving important historical trends. Popper acknowledges that institutions are not simply machines and can have unique characteristics beyond their practical purpose. This chapter also introduces Popper's distinction between two different methods of understanding things: methodological essentialism and methodological nominalism, of which he favors the latter. Methodological essentialism is the view that science should aim to uncover the hidden reality or essence of things through intellectual intuition and to describe it in words through definitions. Methodological nominalism, by contrast, emphasizes the importance of describing how things behave in different situations, and especially whether there are any regularities in their behavior. According to Popper, natural sciences mostly use methodological nominalism, while the social sciences still rely on essentialist methods, which is one of the reasons for their backwardness. Popper notes that some people argue that the difference in method between natural and social sciences reflects an essential difference between the two fields, but he disagrees with this view. Plato's Descriptive Sociology Chapter 4, "Change and Rest", describes Plato's sociology as based on the theory of Forms and universal flux and decay. It is long, and divided into five parts. According to Popper, Plato believed change can only lead towards imperfection and evil, which is a process of degeneration – he saw history as an illness, and set out a system of historical periods governed by a law of evolution. Plato's ideal state was not a progressive Utopian vision of the future, but rather a historical or even pre-historical one that attempted to reconstruct ancient