 THEOPHILUS: These ideas, which are said to come from more than one sense – like those of space, figure, motion – come rather from the common sense, which is to say, from the mind itself; for they are ideas of the pure understanding, though ones which relate to the external world and which the senses make us perceive, and so they admit of definitions and demonstrations. (New Essays, 128; see Leibniz 1840, 230)