 Axioms 4 and 5 define continuous change. Axiom 4 defines the Trajectory predicate. To see what it says, let’s consider a situation of running a mile where \(f_1\) is instantiated by running and \(f_2\) by distance\((x)\). Should running be true during the whole interval from \(t\) until \(t'\) then distance\((a + 1)\) will be true at \(t'\). The value of \(x\), that is, the actual distance actually run at each time instant will be determined by the law of the process under consideration (here, running speed). Axiom 5 defines the predicate Clipped\((t, f, t')\) which is true if \(f\) is terminated or released by an event \(e\) which happens in the time interval between \(t\) and \(t'\). Thus Clipped covers both instantaneous and continuous change. The axioms provide a general theory of what can change and what stays constant.