 To get clear about the idea of power or necessary connection, we need to determine the impressions that are its source. Hume identifies three possible sources in the work of his predecessors: Locke thought we get our idea of power secondarily from external impressions of the interactions of physical objects, and primarily from internal impressions of our ability to move our bodies and to consider ideas. Malebranche argued that what we take to be causes of the motion of bodies or mental activity aren’t causes at all. They are only occasions for God, the sole source of necessary connection, to act in the world. Hume rejects all three possibilities.