Max Weber aimed to make sociology objective and systematic, like the natural sciences. This was a challenge since historical and social reality, the subject matter of sociology, is inherently chaotic and dependent on individual - possibly idiosyncratic or irrational – events and on the subjective interpretations of those events by the contemporary and the subsequent societies and by historians and sociologists. The research and analysis methods of natural scientists would not have worked in sociology. Therefore, he created a conceptual tool called the pure-type.
The pure-type is formed by synthesizing the characteristics and elements of many real-world manifestations of a particular phenomenon into a unified analytical construct that defines the general and logically-consistent features of that phenomenon. For example, Weber studied capitalism and integrated the distinctive features of this economic system across cultures and time-periods to create a pure-type. According to this pure-type, the attributes of capitalism are – pursuit of profit as the sole objective, private ownership of all potential means of profit, competition between companies, and a laissez faire government that does not interfere with the free markets.
A pure-type is not meant to describe all the characteristics of any one instance of a phenomenon. Moreover, no single instance fully adheres to the pure-type. The present-day United States is regarded as the most capitalist nation in world history; however, it too deviates significantly from Weber's pure-type of capitalism. For example, the country has many markets that are dominated by a single large company and hence, are not competitive. The value of a pure-type of capitalism is that it defines the features on which the economic systems of various countries may be objectively compared and on which the changes in the economic system of a country over time may be objectively measured.
(Adapted from the notes of two professors on Weber's theories: www.faculty.rsu.edu and www.ualr.edu)