The theory contained in his book is not to furnish principles for making a new Constitution, but for illustrating the principles of a Constitution already made. It is a theory drawn from the _fact_ of our government. They who oppose it are bound to show that his theory militates with that fact; otherwise, their quarrel is not with his book, but with the Constitution of their country. 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. Allow that to be the true policy of the British system, then most of the faults with which that system stands charged will appear to be, not imperfections into which it has inadvertently fallen, but excellencies which it has studiously sought. 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. _Finita_ potestas denique _cuique_ Quanam sit ratione, atque alte terminus hærens?