Locke devotes a whole chapter - Chapter xxi of Book II, the longest in the Essay - to the idea of power. After a few remarks on power in general, this chapter contains an extensive account of two particular powers belonging to human beings, the power of willing and the power of acting freely. But power also appears at several other places in the Essay. The qualities of material substances, treated in E II.viii and elsewhere, are powers for Locke; the mental operations, described in E II.ix-xi, of which we have ideas of reflection, are exercises of powers of the mind, which Locke calls faculties; and ideas of powers also “make a great part of our complex ideas of substances” (E II.xxiii.7ff.).

In this chapter I propose, first, to consider Locke's conception of power in general; second, to sketch his views of qualities, faculties, and substances; third, to lay out his accounts of the will and of freedom; and finally to outline his views on motivation, which are connected to his treatment of the will and of freedom and which take up a large part of Chapter xxi. Since qualities and substances are being treated in other chapters in this volume, I shall deal very briefly with these two topics, and concentrate most of my attention on power in general and on the particular powers of will and freedom.