  Ward’s criticizes Clifford’s theory on three main accounts. (1) In the first place, the whole theory presupposes a point-to-point correspondence between matter and mind. Clifford’s conception of an atom, however, is obsolete: ‘if the speculations of Lord Kelvin and others are to be accepted, and the prime atom itself is a state of motion in a primitive homogeneous medium [the ether], what is the mental equivalent of this primordial medium?’ (114) In other words, Clifford’s theory couples material atoms with simple ideas. But if the atom is not a simple particle but a state of an underlying substance, it is not so easy to see what precisely in our consciousness could correspond to it.