An Essay Concerning Human Understanding
By John Locke
Book II — Ideas
The idea of the beginning of motion is one that we get only from reflection on what happens in ourselves, where we find by experience that merely by willing something – merely by a thought of the mind – we can move parts of our bodies that have been at rest. So that it seems to me that our sensory perception of the operations of bodies gives us only a very imperfect and obscure idea of active power, since it provides no idea of the power to begin any action, whether physical or mental. If you think you have a clear idea of power from your observations of colliding bodies, I shan’t quarrel with you, because sensation is one of the ways by which the mind gets its ideas. But I thought it worthwhile to consider – just in passing – whether the mind doesn’t receive its idea of active power more clearly from reflection on its own operations than from any external sensation.