This paper temporarily sheds formal mathematical treatment and presents a more intuitive overview of inference mechanisms for quantified relations. These predicate logic expressions are a new class of design constraint among sets of variations affecting the design and performance of engineering systems. Simple examples illustrate the use of quantified relations to infer constraints on the membership of feasible sets. A small design problem from the electronics domain joins the mathematical tools with engineering concepts. A brief comparison demonstrates the advantages of this approach over conventional interval mathematics. This paper’s objective is to illustrate the application of quantified relations and their associated methods to engineering design problems.