But in those disputes, besides the question of the place that belongs to science in relation to religious faith, or to mundane science in relation to revealed and divine science, the question of the nature of the concept was also raised; that is to say, they continued the Platonic-Aristotelian enquiry into the doctrine of the concept in the second of the meanings that we have distinguished. But no true conclusion was reached in this enquiry. The conciliatory formula of the Arabic interpreters of Aristotle, accepted by Albertus Magnus and Thomas Aquinas, in which the universals were affirmed as existing _ante, in_ and _post rem,_ in so far as it is possible to confer upon it an exact meaning, was understood in a superficial manner, and therefore it has not unreasonably seemed too easy and too expeditious.[10] A dispute of this sort cannot be solved by summarizing discordant opinions, as in the formula we have mentioned, or by fixing a mean, as in conceptualism. But the realists, bravely maintaining the truth of the philosophic universal, maintained the rights of rational thought and of philosophy; and the nominalists, on their part, asserting in contradiction to the former, the nominalist universal, prepared the modern theories of natural science. Realism produced philosophic thought of high importance, as in the so-called ontological argument of Anselm of Aosta, which (though through the myth of a personal God) asserts the unity of Essence and Existence, the reality of what is truly conceivable and conceived. Gaunilo, who confuted and satirized that concept, by employing the example of a "most perfect island," thinkable yet non-existent, seems an anticipation of Kant; at least of the Kant who employed the example of the hundred dollars to illustrate the same case--if it is not more accurate to say that Kant was, in that case, a late Gaunilo. Anselm replied (as Hegel did to Kant) that it was not a question of an island (or of a hundred dollars of something imaginable that is not at all a concept), but of the being than which it is impossible to think a greater and a more perfect (the true and proper concept). On the other hand, the nominalists, who like Roscellinus maintained that the _universelles substantiae_ were _nonnisi flatus vocis,_ performed the useful office of preventing the sciences of experience from being absorbed and lost in philosophy. In Roger Bacon we see clearly the connection of nominalism with naturalism. He considered individual facts, so-called external experience, in its immediacy, as the true and proper object of science. Concepts were for him a simple expedient, directed towards the mastery of the immense richness of the individual. "_Intellectus est debilis_ (he said); _propter eam debilitatem magis conformatur rei debili, quae est universale, qitam rei quae habet multum de esse, ut singulare._" [Sidenote: _Nominalism, mysticism and coincidence of opposites._]