  With concepts of natural properties and substances like heat and water we have two reasons for thinking that the corresponding properties may be different. First, the concept of heat seems metaphysically superficial and incomplete. It is the concept of a property that has certain characteristic effects on us and on other things, but does not aim to tell us about the nature of the property that has those effects. The concept of water seems superficial in the same way. This concept only picks out certain surface features of water, such as its being clear, odourless, tasteless, etc. It does not, however, tell us anything about the nature of the substance that has these features. In both cases empirical science seems well-suited to complete this picture by investigating the property or substance that has these distinctive effects, or surface features. In doing this, empirical science provides us with an account of heat and water which is metaphysically deeper than the one provided by the corresponding concepts.