The unity of science is a thesis in philosophy of science that says that all the sciences form a unified whole.
Even though, for example, physics and sociology are distinct disciplines, the thesis of the unity of science says that in principle they must be part of a unified intellectual endeavor: science. The unity of science thesis is often associated with a framework of levels of organization in nature, where physics is the most basic, chemistry the level above physics, biology above chemistry, sociology above biology, and so forth. Further, cells, organisms, and cultures are all biological, but they represent three different levels of biological organization.
It has also been suggested (for example, in Jean Piaget's 1918 work Recherche) that the unity of science can be considered in terms of a circle of the sciences, where logic is the foundation for mathematics, which is the foundation for mechanics and physics, and physics is the foundation for chemistry, which is the foundation for biology, which is the foundation for sociology, the moral sciences, psychology, and the theory of knowledge, and the theory of knowledge is based on logic.
The unity of science thesis is famously clarified and tentatively argued for by Ludwig von Bertalanffy in "General System Theory: A New Approach to Unity of Science" (1951) and by Paul Oppenheim and Hilary Putnam in "Unity of Science as a Working Hypothesis" (1958). It is famously argued against by Jerry Fodor in "Special Sciences (Or: The Disunity of Science as a Working Hypothesis)" (1974), by Paul Feyerabend in Against Method (1975) and later works, and by John Dupré in "The Disunity of Science" (1983) and The Disorder of Things: Metaphysical Foundations of the Disunity of Science (1993).