 Underlying Clarke’s categories and his rejection of the possibility that wholes have properties not possessed by their parts is a principle that from material properties such as magnitude, motion, or solidity, only other material properties, or properties of the same kind, may result. The same kind of restriction can be said to apply to mental properties. Call this the Homogeneity Principle. This Principle, in turn, is related to what has been called an heirloom theory of causality. The idea here is that whatever ends up in an effect, must have been in the cause of that effect. Otherwise one gets contradictions such as that something has come from nothing, or there is more of a given property in the whole than there is in the parts, and so  on.[3]  Later, in “A Third Defense of an Argument” Clarke calls Collins’s attention to the fact that in his proof for the existence of God in Book IV of An Essay Concerning Human Understanding, Locke invokes the Homogeneity Principle to argue that an eternal, immaterial thinking being could not arise from matter (Clarke 1738 [1928: 837]; Clarke and Collins, 2011: 170–171). Clarke holds that this puts an end to Locke’s claim that God could as easily make matter organized in the right way to think. We will return to this when we consider the outcome of the debate.