The functionalist thoery can be traced to a movement in the late nineteenth-century under the influences of Darwinism on the biological and social sciences. It is an attempt to understand the world, and it tests the cause and effect of sociological behavior. Some of the more famous functionalists are Charles Darwin, Emile Durkheim, and Horace Kallen. Horace Kallen's article in the article in the Encyclopedia of the Social Sciences, states that functionalism has influenced every discipline. In psychology, it led to the substitution of the stream of consciousness for states of mind. In philosophy, it led to the rise of pragmatism and instrumentalism, and in logic it replaced the laws of thought with the theory of scientific method. Functionalism basically came to be seen as a means to an end. There are two major sub-schools of modern functionalism; macro-functionalism and micro-functionalism. Macro-functionalism focuses primarily on breaking down large scale systems such as societies or civilizations and making them into small scale systems, such as groups. Micro-functionalism deals mainly with the behaviors and personalities of the group. Functionalism has not fully been accepted because it is a theory that is still developing and is still trying to be understood. Conflict theory is the belief that change and conflict are good for societyflict theorists such as Karl Marx, David Hume, and Adam Ferguson believe that every society requires a minimum realistic view about its conflicts in order to survive. In Adam Ferguson's An Essay on the History of Civil Society, he states that the conflict theory of society has reevaluated the importance of specific institutions so that social order can be maintained. He suggested that revolts were beneficial and that the elimination of state would move society in a foward direction. Some of the reasons that the conflict theory was not completely successful were due to the fact that not many social scientists were thrilled about the idea of replacing the state with a bureau of sociologists.