 When a property (relation) is predicable of some objects will be determined by a number of principles (or axioms) (Johnston 2006: 685). For example, particulars are not predicable of other particulars, n-place properties are only predicable of n particulars. It is part of the nature of the objects and properties on which a state of affairs ontologically depends that the properties are predicable of the objects. This brings us to a key thought of Wittgenstein’s theory of states of affairs. He wrote in the Tractatus Logico-Philosophicus: