This idea of a balanced constitution can be traced back to Aristotle, but it first seems to have been put forward in modern times by King Charles I, in His Majesties Answer to the Nineteen Propositions (1642):
There being three kindes of Government amongst men, Absolute Monarchy, Aristocracy and Democracy, and all these having their particular conveniencies and inconveniencies. The experience and wisdom of your Ancestors hath so moulded this out of a mixture of these, as to give to this Kingdom (as far as human prudence can provide) the conveniencies of all three, without the inconveniencies of any one, as long as the Balance hangs even between the three Estates, and they run jointly on in their proper Chanell.... The ill of absolute Monarchy is Tyrannie, the ill of Aristocracy is Faction and Division, the ills of Democracy are Tumults, Violence and Licentiousnesse. The good of Monarchy is the uniting a Nation under one Head to resist Invasion from abroad, and Insurrection at home. The good of Aristocracie is the Conjuncion of Counsell in the ablest Persons of a State for the publike benefit. The good of Democracy is Liberty, and the Courage and Industrie which Libertie begets.
In this Kingdom the Laws are jointly made by a King, by a House of Peers, and by a House of Commons chosen by the People, all having free Votes and particular Priviledges. The Government according to these Laws is trusted to the King.... And this kinde of regulated Monarchie having this power to preserve that Authoritie, without which it would be disabled to preserve the Laws in their Force, and the Subjects in their Liberties and Proprieties, is intended to draw to him such a Respect and Relation from the great Ones, as may hinder the ills of Division and Faction, and such a Fear and Reverence from the people, as may hinder Tumults, Violence, and Licenciousnesse. Again, that the Prince may not make use of this high and perpetuall power to the hurt of those for whose good he hath it, and make use of the name of Publike Necessitie for the gain of his private Favourites and Followers, to the detriment of his People, the House of Commons (an excellent Conserver of Libertie, but never intended for any share in Government, or the chusing of them that should govern) is solely intrusted with the first Propositions concerning the Levies of Moneys... and the Impeaching of those, who... have violated [the] Law.... And the Lords being trusted with a Judicatory power, are an excellent Screen and Bank between the Prince and People, to assist each against any Incroachments of the other, and by just Judgements to preserve that Law, which ought to be the Rule of every one of the three.The theme later appeared in An argument shewing that a standing army is inconsistent with a free government and absolutely destructive to the constitution of the English monarchy by John Trenchard and Walter Moyle (1697):
Our Constitution is a limited mix'd Monarchy, where the King enjoys all the Prerogatives necessary to the support of his Dignity, and Protection of his People, and is only abridged from the Power of injuring his own Subjects.... [O]ur Government may truly be called an Empire of Laws, and not of Men; for every Man has the same right to what he can acquire by his Labour and Industry, as the King hath to his Crown, and the meanest Subject hath his Remedy against him in his Courts at Westminster. No Man can be imprisoned, unless he has transgressed a Law of his own making, nor be try'd but by his own Neighbours....Another affirmation of the doctrine is found in Henry St. John Bolingbroke's Remarks on the History of England (1743):
And lest the extraordinary Power intrusted in the Crown should lean towards Arbitrary Government, or the tumultuary Licentiousness of the People should encline towards a Democracy, the Wisdom of our Ancestors hath instituted a middle State, viz. of Nobility, whose Interest it is to trim this Boat of our Commonwealth, and to screen the People against the Insults of the Prince, and the Prince against the Popularity of the Commons, since if either Extream prevail so far as to oppress the other, they are sure to be overwhelmed in their Ruin. And the meeting of these three States in Parliament is what we call our Government: for without all their Consents no Law can be made, nor a Penny of Money levied upon the Subjects.... [T]he Excellence of this Government consists in the due ballance of the several constituent Parts of it, for if either one of them should be too hard for the other two, there is an actual Dissolution of the Constitution, but whilst we can continue in our present Condition, we may without vanity reckon our selves the happiest People in the World.
If the legislative, as well as the executive Power, was wholly in the King, as in some Countries, he would be absolute; if in the Lords, our Government would be an Aristocracy; if in the Commons, a Democracy. It is this Division of Power, these distinct Privileges attributed to the King, to the Lords, and to the Commons, which constitute a limited Monarchy.Blackstone endorsed the doctrine in his Commentaries:
Again, as they constitute a limited Monarchy, so the Wisdom of our Government has provided, as far as human Wisdom can provide, for the Preservation of it, by this Division of Power, and by these distinct Privileges. If any one Part of the Three, which compose our Government, should, at any Time, usurp more Power than the Law gives, or make an ill use of a legal Power, the other two Parts may, by uniting their Strength, reduce this Power into its proper Bounds, or correct the Abuse of it; nay, if at any Time two of these Parts should concur in usurping, or abusing Power, the Weight of the third may, at least, retard the Mischief, and give Time and Chance for preventing it.
This is that Ballance, which has been so much talk'd of; and this is the Use of it. Both are plain to common Sense, and to Experience....
And herein indeed consists the true excellence of the English government, that all the parts of it form a mutual check upon each other. In the legislature, the people are a check upon the nobility, and the nobility a check upon the people; by the mutual privilege of rejecting what the other has resolved: while the king is a check upon both, which preserves the executive power from encroachments. And this every executive power is again checked, and kept within due bounds by the two houses, through the privilege they have of enquiring into, impeaching, and punishing the conduct (not indeed of the king, which would destroy his constitutional independence; but, which is more beneficial to the public) of his evil and pernicious counsellors. Thus every branch of our civil polity supports and is supported, regulates and is regulated, by the rest; for the two houses naturally drawing in two directions of opposite interest, and the prerogative in another still different from them both, they mutually keep each other from exceeding their proper limits; while the whole is prevented from separation, and artificially connected together by the mixed nature of the crown, which is a part of the legislative, and the sole executive magistrate. Like three distinct powers in mechanics, they jointly impel the machine of government in a direction different from what either, acting by themselves, would have done; but at the same time in a direction partaking of each, and formed out of all; a direction which constitutes the true line of the liberty and happiness of the community.So did Edmund Burke in his Appeal from the New to the Old Whigs:
The whole scheme of our mixed constitution is to prevent any one of its principles from being carried as far, as taken by itself, and theoretically, it would go.... To avoid the perfections of extreme, all its several parts are so constituted, as not alone to answer their own several ends, but also each to limit and control the others: insomuch, that take which of the principles you please — you will find its operation checked and stopped at a certain point. The whole movement stands still rather than that any part should proceed beyond its boundary. From thence it results, that in the British constitution, there is a perpetual treaty and compromise going on, sometimes openly, sometimes with less observation. To him who contemplates the British constitution, as to him who contemplates the subordinate material world, it will always be a matter of his most curious investigation, to discover the secret of this mutual limitation.Bagehot, however, was having none of it. He wrote in The English Constitution:
There are two descriptions of the English Constitution which have exercised immense influence, but which are erroneous. First, it is laid down as a principle of the English polity, that in it the legislative, the executive, and the judicial powers, are quite divided — that each is intrusted to a separate person or set of persons.... Secondly, it is insisted that the peculiar excellence of the British Constitution lies in a balanced union of three powers. It is said that the monarchical element, the aristocratic element, and the democratic element, have each a share in the supreme sovereignty, and that the assent of all three is necessary to the action of that sovereignty. Kings, lords, and commons, by this theory, are alleged to be not only the outward form, but the inner moving essence, the vitality of the constitution. A great theory, called the theory of “Checks and Balances,” pervades an immense part of political literature, and much of it is collected from or supported by English experience. Monarchy, it is said, has some faults, some bad tendencies, aristocracy others, democracy, again, others; but England has shown that a government can be constructed in which these evil tendencies exactly check, balance, and destroy one another — in which a good whole is constructed not simply in spite of, but by means of, the counteracting defects of the constituent parts.
Accordingly, it is believed that the principal characteristics of the English Constitution are inapplicable in countries where the materials for a monarchy or an aristocracy do not exist. That constitution is conceived to be the best imaginable use of the political elements which the great majority of States in modern Europe inherited from the mediaeval period. It is believed that out of these materials nothing better can be made than the English Constitution; but it is also believed that the essential parts of the English Constitution cannot be made except from these materials. Now these elements are the accidents of a period and a region; they belong only to one or two centuries in human history, and to a few countries. The United States could not have become monarchical, even if the Constitutional Convention had decreed it, even if the component States had ratified it. The mystic reverence, the religious allegiance, which are essential to a true monarchy, are imaginative sentiments that no legislature can manufacture in any people. These semi-filial feelings in government are inherited just as the true filial feelings in common life. You might as well adopt a father as make a monarchy; the special sentiment belonging to the one is as incapable of voluntary creation as the peculiar affection belonging to the other. If the practical part of the English Constitution could only be made out of a curious accumulation of medieval materials, its interest would be half historical and its imitability very confined.Bagehot, of course, believed that the monarchy and the Lords were "dignified" rather than "efficient" parts of the constitution. He has been criticised for underestimating the still very real power of the Victorian monarchy, but what he said certainly became the truth, even if it was somewhat inaccurate at the time.