Theory or the Doctrine of separation of power originated from Aristotle and was further developed by John Locke and was popularised by the French philosopher Montesquieu in his book ‘De L‘Espirit des Lois ’ in the year 1748. This theory became an essential source for the maintainability of the three pillars or the organs of government namely legislative, executive, and judiciary, with the functions to make laws, execute those laws and interpret those laws respectively. According to the concept of separation of powers, the three organs of a government are not to encroach upon each other’s functions and are to carry out their duties separately with interference from each other as, a fusion of legislative and executive powers would lead to despotism prevailing in the governance of a state and similarly, the union of legislative and judicial powers would also lead to a situation of imbalance in the governance.
The main aim of the concept arrived at from the theory is that concentration of powers in a particular Head of the government would lead to dictatorship and despotism by the head of the government which is proved true for all times and ages and this theory aims at liberty and acts as a perfect check and reprimands the executive and administrative organs of the government to proceed through the process of law and justice. Thus the separation of powers theory given by Montesquieu can be said to be based on the English system of governance where the law is supreme (lex supremus).
Reason(supposed reason) why Separation of power aims at Liberty and is (believed) to be based on the English system of governance:
The reason why separation of power mainly aims at individual liberty may be that the period when Philosopher Montesquieu had existed was a time in the European atmosphere where the ignition for revolutions and the time-period before the Enlightenment and French revolution era had started building up ideologies of liberty, fraternity, and equality in people and during this period the concept of Individual liberty was building up and had played a great role in the revolutions in France. During those periods, Monarchy was the most prevalent form of government whereby all the administrative powers of a state were in the hands of the Monarch which most of the time leads to despotism and dictatorship as the laws were made to benefit the Monarch and the rights of its citizens were not properly recognized.
And the reason why separation of power is believed to be based on the English system of governance is that it expresses the Principle of Supremacy of law concerning the governance of a state. The Monarch and the cabinet perform executive functions, the parliament performs the legislative functions, and the judiciary is taken care of by the law courts, which brought out the execution of separation of powers. Separation of powers acted as a better alternative when against Monarchy.
Separation of power in the United Kingdom:
Although when traced out, the UK system of administration looks to be based on the separation of power theory a closer look shows that the British system is based on the fusion of Parliament and the Monarch where the Ministers of parliament perform dual functions of Executive as well as legislation, Prime minister can dissolve house of Commons (parliamentary House) and, The parliament can dismiss the Cabinet, lord chancellor who is head of Judiciary is considered an essential member of Cabinet and the crown summons and can dissolve house of Commons(parliamentary House). This shows that all three organs of the government keep a check on each other and are not in connection with the Doctrine of Separation of powers in Reality thus, Britain does not follow the Doctrine of Separation of Power in an Absolute sense but rather in a flexible manner.
Separation of power in India and the United States of America:
Articles 1,2& 3 of the US constitution provide for Separation of power whereby the legislature is under the congress, the Executive is under the power of the President, and the Judicial powers are vested in its Courts with Supreme Court being the head of the Judiciary.
In India, the constitution provides for a parliamentary form of government whereby the Legislation is under the control of parliament, the Executive is under the President and the Council of Ministers, and the Judiciary is under Supreme Court and the High Courts.
It can be said that the Indian Constitution does not follow the doctrine of Separation of powers in its absolute form but the functions of the three organs of government have been sufficiently differentiated for the functioning of this quasi-federal country, as the President of India who is the head of the Executive is vested with the powers to issue an ordinance which is a function of Legislation and the Lok Sabha has a vote of no-confidence to keep the Executive functioning vigilantly. But the Judiciary has an upper hand on both Executive and Legislation as it has Independence of Carrying out its functions and has been recognized as the basic structure of the Constitution. The provisions of the Indian constitution from Articles 124-147 and Articles 214-231 deal with the appointment of Supreme court and High courts judges respectively, which, in a literal sense shows the independence of the judiciary in the appointment of its members although, NJAC which was introduced for the appointment of judges with the commission members consisting of Executive and legislative members including judicial Members for the appointment of judges but was later ruled unconstitutional as it was found violative of the Basic Structure of the Indian Constitution. And Judicial Review is a powerful Function in the Hands of the Indian Constitution which grants the Supreme Court of India to review any Act passed by the Legislation or any bills accepted by the Executives. The main check for Judiciary is in the Impeachment of its judges. This thus shows that the Separation of power is not followed in an absolute sense, since it is not to violate the Doctrine of Basic Structure of Constitution as The Constitutional supremacy is to be maintained.
Whereas, In the US the Doctrine of separation of powers is followed in a rigid sense whereby the Branches of the government have been particularly divided and are vested with functions and duties separately as it is as such provided in their Constitution. In Wayman Vs. Southard, it was held that the Congress cannot Delegate its function to Judiciary as it is violative of the Constitutional provisions and thus such Delegation was held Unconstitutional. the Branches of the government function according to the Separation of powers Adopted by its Constitution and thus to prevent Arbitrariness in these Branches, the system of checks and balances has been used. The system of checks and balances acts as an extension of separation of powers as it further smoothens down the concept laid down by separation of power. As per the Principle of Check and Balances, the organs of government by having separation of power act as a natural check on each of its Organs and maintain the balance of power between these organs of the government.
From what has been observed the US follows the Doctrine of Separation in its Absolute form whereas India does not follow the Doctrine in its Absolute form. The reason for this is that the Doctrine of Separation of Powers was not provisioned in its Constitution but was taken up as Doctrine followed from the British system of Administration which follows parliamentary supremacy but, India follows Parliamentary form of Government with Independence of Judiciary which is a combination that thrives for Judicial review and Interdependence of the organs of government in creating a check and balance system as that of the US, where, Judiciary is given supremacy.
Thus, the Expectations which arise from the Doctrine of Separation of power are different from the reality which is there. Separation of power Aims for the Branches of a government to not encroach upon each other and maintain Individual liberty as the supreme course of law but with concepts of Independence of Judiciary, Judicial Review the branches of government Try and keep a check on each other’s powers and try maintaining to balance out the power struggle between these branches to curb the arbitrariness.
Therefore to conclude, The theory of Separation of Powers that was given out by the French philosopher Montesquieu in his book spirit of laws in 1748 based on the views of the time when revolutions and major happening in Europe took place, cannot be unfolded to its full extent, Since to keep a check on despotic governance a limited amount of encroachment is needed as it is required for maintaining of the branches of government thus Separation of powers as followed in Reality is flexible and is further smoothened out by the system of Check and Balances and Maintains the Independence of Judiciary and Judicial review and also has a well-differentiated organ of Government that provides for the Doctrine of Separation of Power that helps solve issues of social, economic and cultural problems which are sometimes hindered by Separation of powers.
 Supreme Court Advocates-on-record Association & Anr. vs. Union of India, (2016) 5 SCC 1, (2016) 2 SCC (LS) 253.
 Indira Nehru Gandhi Vs. Raj Narain, 1975 AIR 1590, 1975 SCC (2) 159.
 Kesavananda Bharati Sripadagalvaru & Ors. v. State of Kerala & Anr., Writ petition(civil) 135 1970.
 Wayman Vs. Southard, 23 U.S. 10 Wheat. 1 1 (1825).