 In the light of the geometric example, Weyl attacks the concept “defined by means of finitely many words” as not precise, and long before Fraenkel and Skolem, he succeeds in making the separation principle precise: he simply replaces Zermelo’s informal concept of definite property with the notion of ‘relation explicitly definable from extensional equality and membership by means of the basic elementary logical principles’ (we should simply say: first-order definable).