 CL was originally invented as a continuation of the reduction of the set of logical constants to a singleton set in classical first-order logic (FOL). CL untangles the problem of substitution, because formulas can be prepared for the elimination of bound variables by inserting combinators. Philosophically speaking, an expression that has no bound variables represents the logical form of the original formula. Sometimes, bound variables are thought to signify “-->ontological commitments-->.” Another philosophical rôle of CL is to show the variability of the ontological assumptions a theory has.