The separation of powers is a doctrine that proceeds from the assertion of the need to divide the state (in the broad sense - any other) power into autonomous and mutually controlling branches. With regard to the state power, it is supposed to be divided into the legislative branch, executive and judicial.
The constitutional principles of the separation of powers were first proposed as a right-idea by J. Locke in his theory of “social contract”. This happened in 1689. As a political and legal category, principles became widespread in the mid-18th century after the appearance of the works of S.-L. Montesquieu.
However, one should not assume that this time is the period of the practical beginning of the implementation of the idea. Some principles or their elements are found in the theoretical development of ancient thinkers. So, even Aristotle suggested dividing power into branches, only as such he cited the legislative, judicial and official, where each of the branches is headed by a separate body.
The principles of separation of powers as a legal norm were implemented in the US Constitution, and the authors, the "founding fathers", also singled out the principle of "vertical" division, which was supposed to regulate relations between the federal center and the states. By the beginning of the 19th century, the principles of separation of powers were quite widely recognized as one of the leading postulates of state law science, which nevertheless continued to develop, for example, in some countries the list of principles was interpreted broadly - the constituent, control ones also stood out as independent selective branches.
As a political and legal idea, the principle of separation of powers suggests that their very presence in law and practical implementation are the basis for the construction and functioning of a modern state.
The principles of separation of powers imply a number of organizational and substantive decisions that are basic in the construction of the state model and law. They provide that each of the types of power is exercised by specially created bodies of power: legislative - by parliament, executive - by executive authorities (cabinet of ministers), judicial - by the judicial system. At the same time, the relative independence of the activities of all these institutions is affirmed, which is technically realized through the separation of powers and the areas of application of these powers.
The functions of the authorities are distributed in such a way that the powers of the authorities are not duplicated in the actions of their bodies, and also that each of the branches can to some extent control the other branch. In states with a multilevel system for constructing the form of state-territorial structure (federations), in addition, a clear distribution of powers between the authorities of the center and the regions that make up this state is also provided. The modern model of separation of powers also contains a requirement to ensure a legal balance between branches. This is done in order to prevent the legal dominance of one branch over another and, thus, not lead the state to the establishment of a totalitarian political regime, for which just such a design is characteristic.
The principles stipulate the need to build such a mechanism for exercising power in which the branches will mutually restrain each other due to the legislatively distributed powers of mutual control and balance by clearly establishing the subject of their authority for each branch.
Today, the idea of separation of powers is a universally recognized principle of building a modern state and is implemented to one degree or another in almost all countries of the world where the presence of democratic principles in this area has developed. Some countries use the classical model, while in others, the application of these principles is mediated by national traditions of building a state and culture. For example, in China, in addition to traditional branches, such branches as the control and legal branches are also distinguished. The situation is the same in Taiwan.
In states where totalitarian-authoritarian political regimes have developed , the principles of separation of powers are either not implemented at all or are formally implemented.