21. The formal system of cardinal numerals, as used in Classical Arabic, is extremely complex. 22. There may be a formal system , with due process and the rule of law. 23. The basic objects of metalogical study are formal languages, formal systems , and their interpretations. 24. A formal system is used to derive one expression from one or more other expressions. 25. Propositional and predicate calculi are examples of formal systems . 26. *This is a fine example of a formal system . 27. A formal system might be syntactically incomplete by design : such as logics generally are. 28. The Russians want a formal system in place that could include inspections of weapons sites. 29. In a formal system a symbol may be used as a token in formal operations. 30. Mathematical logicians study formal systems but are just as often realists as they are formalists.
