 But even if we put aside Frege’s notation for complex formulas, it is important to point out that Frege didn’t use atomic formulas of the form \(Px\), \(Rxy\), etc., as we have done. Instead of including \(n\)-place relation names and variables among his primitive terms, he included primitive function names and variables such as \(f\), \(g\), \(h\), …, and used them to signify functions. That is, instead of distinguishing objects and relations, Frege distinguished objects from functions. Though some developments of the modern predicate calculus include function terms among the simple terms of the language, we have not included them because we shall not need them in the development of Frege’s Theorem.