  So we may say that both a fire and a building have extent, divisibility and so on, but that a building has some properties, such as grayness, that fire lacks and that fire has some properties, such as luminance, that the building lacks. It may be that some of the properties that some but not all particular bodies have are to be understood in terms of primary qualities, but Holbach does not insist on this point. The properties which Locke called secondary qualities are not distinguished from primary qualities by the fact that they are rightly understood in terms of them. Rather, the only distinction between these properties and primary qualities is that primary qualities are in all matter alike and secondary qualities are in only some bodies. Of fire, for example, Holbach writes: