Michel Foucault's The Order of Things is not a "traditional" history text. He abandons the diachronic historical conceptions of periods and progress for a synchronic descriptive method. Foucault shows that human knowledge follows a discursive structure, an "episteme." The episteme is what makes it possible to know and to speak at a given time through ordering the world in a particular way in a particular period. Due to the episteme, different disciplines look more like each other in one period than the same discipline in another period. Scholars did not see that they all employed the same rules to define their objects as the other disciplines of their period. By showing that disciplines in the same time use the same mode of knowing, which is different than those same disciplines in another episteme, Foucault can argue that man, the subject, is a product of history, a particular formation in history. But almost more importantly for us here, even though Foucault approaches history by examining the renaissance, the enlightenment, the modern, and the post-modern eras, he resists positing a strict or definite break between the latter two modes of thought. For a quick summary of The Order of Things in relation to the rise of man see below. For a discussion of the demarcation between modernism and postmodernism see PUNK.

The mode of knowing in the renaissance was resemblance. To have knowledge, to know, it was necessary to speak through the ordering principle of resemblances. A signifier signified via resemblance, making resemblance knowledge itself. In this period there were no distinct human or natural sciences, because there was no distinction between man and world. God put man, nature, and language all in the world, so they were given equal status. Thus, there were endless potential resemblances for man to interpret. Everything could find something that it resembled and by doing so everything could find a meaning. All was ordered. This is why magic and knowledge were acceptable. Both were possible because knowledge was likeness. The signifier equaled similitude. In this episteme words were in the world the same way man and things were in the world. They all had the same value because they were put in the world by God. 

As soon as the mode of knowing of the 16th century disappeared, God disappeared. By the 18th century signs no longer resembled what they meant. Signification had come into being. The classical episteme saw words as transparent. Language represented the real nature of things. The signifier equaled the signified. If the sign equaled the world, and human knowing was based on the sign, then the sign equaled human knowing and there was no need for God. Truth was in the object. This made possible the creation and expansion of the natural sciences. The world became an object to be known. But limiting knowledge to observation lead to ordering by external characteristics. Thus, the object of economics was limited to wealth or observable goods, natural history to the exterior parts of plants and animals, and language to grammar. But with words transparent to the object, the emergence of the natural sciences also made language the application of names. As resemblance was the means of ordering knowledge in the renaissance, naming and classification on the basis of exterior visible characteristics performed that function in the enlightenment.

The modern period was marked by internal organic structures as a means of knowledge and ordering the world, rather than characteristics. The notion of abstract forces made economics' object no longer observable wealth, but the hidden force of man's labor. Rather than being transparent or simply grammar, language became an object filled with hidden forces which directed what could be said. And in biology the ordering criteria became internal organs and their functions. But in the modern period, history became the fundamental reality of things. History connected organic structures to one another in a temporal series. Thus, history applied to biology made Darwin's theory of evolution possible, and applied to language generated philology. Consequently, history dealt with things that had their principle being within themselves. As the classical period closed, being was separated from representation allowing being "in itself" to be addressed. However, it was the disappearance of God which cleared the space for man to occupy as the question of his being arose. With man now as an object, the human sciences became possible. But rather than focusing on structural forces, the notion of abstract forces lead to the development of psychology. This allowed psychological man to go inward to the unconscious. Thus, psychology and history were behind the newly formed human sciences of anthropology and sociology, not external structural forces. 

The post modern period was marked by the shift from the introspective subject as the object of the human sciences to their underlying societal structure. Structuralism and the abstract force of signs finally hits the human sciences of psychology and anthropology. This tentatively begins with Freud, Saussure, and structural anthropologists in the early 20th century. According to Foucault, this shift in emphasis is leading to the dehumanization of man. Psychology and anthropology no longer need man as an object of study. Man can no longer retreat inward. The dichotomy of subject and object is offset by language. The space left by God was filled by man, and the space that man is leaving is being filled by language. Subjectivity is a historical phenomenon, and as such is subject to historical transformation.