LIBERTY is a power to act or not to act, according as the mind directs.
 John Locke, An Essay Concerning Human Understanding (1689). copy citation

Context

“Wherein lighting upon a very easy and scarce observable slip I had made, in putting one seemingly indifferent word for another that discovery opened to me this present view, which here, in this second edition, I submit to the learned world, and which, in short, is this: LIBERTY is a power to act or not to act, according as the mind directs. A power to direct the operative faculties to motion or rest in particular instances is that which we call the WILL. That which in the train of our voluntary actions determines the will to any change of operation is SOME PRESENT UNEASINESS, which is, or at least is always accompanied with that of DESIRE.” source