3 Relative of change: variables, pararnet and consbMts ; system first
One element of-the preceding discussion points to a solution to sorre of these difficulties - one which is not yet much evident in applied work. When the differential equations for the ~-variables were introduced, it seemed intuitively correct to make those equations functions of 'pararreters' which we treat as constants for this particular problem. What this means in practice is that these pararreters have rates of change wh i ch are even s lower than those of the .!!.-vari ab les. It woul d easily be possible to extend this argurrent and to develop whole hierarchies of variable classifications.