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Schoolchildren in the US are taught about the division of the US government into three branches: the legislative branch, the executive branch, and the judicial branch. Where did this idea of three separate branches come from? Part of the path is likely to be through John Locke: many of the framers of the US Constitution were well-versed in the works of John Locke.

In Sections 143-144 of his 2d Treatise on Government: Of Civil Government, in Chapter XII, “Of the Legislative, Executive, and Federative Power of the Commonwealth,” John Locke makes the case for separating the Legislative from the Executive power. The centerpiece of his case is that combining the Legislative and Executive power in the same people is too great a temptation for misrule, because it guarantees that those who hold both of these power can avoid being subject to the laws themselves. If the two powers are separated, the Executive can ensure that the members of the legislature are subject to the laws—and, unstated by John Locke in this chapter, there is at least the hope that the legislature can hold the executive accountable through some power of impeachment or vote of no confidence.

Intriguingly, John Locke’s case for separating the executive and legislative power contains an argument for legislatures being out of session most of the time (bolding added below), threaded within his argument that combining the legislative and executive powers is too great a temptation for a ruler or rulers:

§. 143. The legislative power is that, which has a right to direct how the force of the commonwealth shall be employed for preserving the community and the members of it. But because those laws which are constantly to be executed, and whose force is always to continue, may be made in a little time; therefore there is no need, that the legislative should be always in being, not having always business to do. And because it may be too great a temptation to human frailty, apt to grasp at power, for the same persons, who have the power of making laws, to have also in their hands the power to execute them, whereby they may exempt themselves from obedience to the laws they make, and suit the law, both in its making, and execution, to their own private advantage, and thereby come to have a distinct interest from the rest of the community, contrary to the end of society and government: therefore in well-ordered commonwealths, where the good of the whole is so considered, as it ought, the legislative power is put into the hands of divers persons, who duly assembled, have by themselves, or jointly with others, a power to make laws, which when they have done, being separated again, they are themselves subject to the laws they have made; which is a new and near tie upon them, to take care, that they make them for the public good.

144. But because the laws, that are at once, and in a short time made, have a constant and lasting force, and need a perpetual execution, or an attendance thereunto; therefore it is necessary there should be a power always in being, which should see to the execution of the laws that are made, and remain in force. And thus the legislative and executive power come often to be separated.  

John Locke follows this argument for separating the legislative and executive power with an argument for combining the executive and foreign policy power in the same agent. The executive power and foreign policy power differ because, by the idiosyncratic nature of interactions with foreign powers, it is hard to constrain the foreign policy power by legislation to the same extent that the executive power can be constrained by legislation. But both the executive and foreign policy power involve someone acting as an agent for the “public good”: the interests of the people of the commonwealth as a whole. Along the way, John Locke gives a nice description of foreign policy from a philosophical point of view:

§. 145. There is another power in every commonwealth, which one may call natural, because it is that which answers to the power every man naturally had before he entered into society: for though in a commonwealth the members of it are distinct persons still in reference to one another, and as such are governed by the laws of the society; yet in reference to the rest of mankind, they make one body, which is, as every member of it before was, still in the state of nature with the rest of mankind. Hence it is, that the controversies that happen between any man of the society with those that are out of it, are managed by the public; and an injury done to a member of their body, engages the whole in the reparation of it. So that under this consideration, the whole community is one body in the state of nature, in respect of all other states or persons out of its community.  

§. 146. This therefore contains the power of war and peace, leagues and alliances, and all the transactions, with all persons and communities without the commonwealth, and may be called federative, if any one pleases. So the thing be understood, I am indifferent as to the name.  

§. 147. These two powers, executive and federative, though they be really distinct in themselves, yet one comprehending the execution of the municipal laws of the society within itself, upon all that are parts of it; the other the management of the security and interest of the public without, with all those that it may receive benefit or damage from, yet they are always almost united. And though this federative power in the well or ill management of it be of great moment to the commonwealth, yet it is much less capable to be directed by antecedent, standing, positive laws, than the executive; and so must necessarily be left to the prudence and wisdom of those, whose hands it is in, to be managed for the public good: for the laws that concern subjects one amongst another, being to direct their actions, may well enough precede them. But what is to be done in reference to foreigners, depending much upon their actions, and the variation of designs and interests, must be left in great part to the prudence of those, who have this power committed to them, to be managed by the best of their skill, for the advantage of the commonwealth.  

§. 148. Though, as I said, the executive and federative power of every community be really distinct in themselves, yet they are hardly to be separated, and placed at the same time, in the hands of distinct persons: for both of them requiring the force of the society for their exercise, it is almost impracticable to place the force of the commonwealth in distinct, and not subordinate hands; or that the executive and federative power should be placed in persons, that might act separately, whereby the force of the public would be under different commands: which would be apt some time or other to cause disorder and ruin.

For links to other John Locke posts, see these John Locke aggregator posts: 

• John Locke's State of Nature and State of War

• On the Achilles Heel of John Locke's Second Treatise: Slavery and Land Ownership

• John Locke Against Natural Hierarchy

• John Locke's Argument for Limited Government