The authority of the English monarch may be considered from different points of view, which must be taken up in succession; the first question being what power is legally vested in the Crown; the second how much of that power can practically be exercised at all; the third how far the power of the Crown actually is, or may be, used in accordance with the personal wishes of the King, and how far its exercise is really directed by his ministers; the fourth, how far their action is in turn controlled by Parliament. The first two questions, which form the subject of this chapter, cannot always be treated separately, for it is sometimes impossible to be sure whether a power that cannot practically be exercised is or is not legally vested in the Crown. An attempt to make use of any doubtful power would probably be resisted, and the legality of the act could be discussed in Parliament or determined by the law courts; but it is very rare at the present day that any such attempt is made. There are powers that have been disputed, or fallen into disuse, and that no government would ever think of reviving; and thus the question of law never having been settled, the legal right of the Crown to make use of them must remain uncertain. [Sidenote: The Prerogative.] The authority of the Crown may be traced to two different sources. One of them is statutory, and comprises the various powers conferred upon the Crown by Acts of Parliament. The other source gives rise to what is more properly called the prerogative. This has been described by Professor Dicey[18:1] as the original discretionary authority left at any moment in the hands of the King; in other words, what remains of the ancient customary or Common Law powers inherent in the Crown. The distinction is one not always perfectly easy to draw, for many parts of the prerogative have been regulated and modified by statute, and in such cases it is not always clear whether the authority now exercised is derived from statute or from the prerogative. Nevertheless the distinction is often important, because where the powers have been conferred by Parliament the Crown acts by virtue of a delegated authority which lies wholly within the four corners of the statute, and exists only so far as it is expressly contained therein; while the prerogative not being circumscribed by any document is more indefinite, and capable of expanding or contracting with the progress of the suns. [Sidenote: Legislative Power.]