For James Mill, knowledge comes from sense experience. There are two kinds of sensations, he argued. The first kind is experienced when the object of sense is present. The sources of this kind of experience are the senses and the experience of those sensations which accompany muscle and digestive activity. The second kind is experienced when the object of sense is no longer present. Even after the sensation is gone, some sensory content, a “bare fact,” remains: “a copy, an image, of the sensation, sometimes a representation, or trace, of the sensation," i.e. its idea (Mill 1829a, I.40–41). “[D]uring the whole of our lives,” James Mill argued, “a series of those two states of consciousness, called sensations, and ideas, is constantly going on.” He highlighted that ideas do not derive from objects but from sensations. And as sensations are either synchronous or successive, “[o]ur ideas spring up, or exist, in the order in which the sensations existed,” in space (simultaneous existence) and/or in time (antecedent and consequent existence) (Mill 1829a, I.52, 55–56).