It may be observed that of these three modes of change, the first is the most obvious, direct, and effective, but also the most difficult to apply, because it needs an agreement of many independent bodies which is rarely attainable. The second mode is less potent in its working, because an interpretation put on a provision may be recalled or modified by the same authority, viz. the courts of law (and especially the Supreme Federal Court), which has delivered it. But while a particular interpretation stands, it is as strong as the Constitution itself, being indeed incorporated therewith, and therefore stronger than anything which does not issue from the same ultimate source of power, the will of the people. The weakest, though the easiest and most frequent method, is the third. For legislation and custom are altogether subordinate to the Constitution, and can take effect only where the letter of the Constitution is silent, and where no authorized interpretation has extended the letter to an unspecified case. But they work readily, quickly, freely; and the developments to be ascribed to them are therefore as much larger in quantity than those due to the two other methods as they are inferior in weight and permanence.
We shall perceive after examining these three sources of change not only that the Constitution as it now stands owes much to them, but that they are likely to modify it still further as time goes on. We shall find that, rigid as it is, it suffers constant qualification and deflection, and that while its words continue in the main the same, it has come to mean something different to the men of 1890 from what it meant to those of 1810 when it had been at work for more than twenty years, or even to those of 1860, when the fires of protracted controversy might be thought to have thrown a glare of light into every corner of its darkest chamber.
