The proposition that things in themselves are unknowable finds a strong argument in the statement that we can know relations only, that all knowledge is relative. It is undoubtedly true that all knowledge is relative and knowledge is a knowledge of relations. But what is a relation? When I once proposed this question, I was answered: “A relation is the connection between two things; it is that something in which the one stands to the other, in short, it is the betwixtness of things.” This is exactly what a relation is not. From such a definition of relation agnosticism will necessarily follow. It is a misstatement of the case, and when we come to follow out the idea, we shall be led into inextricable contradictions, and unless we revise the whole argument, we shall have to confess that we are at our wit’s end. The question, what is a relation? was one of the issues between the two great mediæval schools of philosophy, the Nominalists and the Realists.[45] The Nominalists answered: “A relation is a mere product of the mind,” while the Realists declared that “a relation without which the thing cannot be, is in the thing.” Both schools relied upon Aristotle’s authority. Aristotle had declared that matter is mere possibility of existence (it is δυνάμει ὄν) and form is that which makes it real, the formal is the real, form is existence or being (οὐσία). The metal of a statue, Aristotle says, is its matter, the idea of the statue is its form, both together make the real statue. The metal having had another form before, did not exist with the inherent purpose of being this metal of the statue. The metal is the mere potentiality of becoming a statue.[46] Hence, says Aristotle, not the matter but the form constitutes the reality of the statue, the form is that which is real, or that which makes actual, ἐνεργείᾳ ὄν, it is the being in completeness or actuality, ἐνετλεχείᾳ ὄν, i. e. that which makes a thing exist in its purpose (ἐν τέλει ἔχειν). If the formal alone is and makes real, relations must be real. This is in favor of the Realists. Yet Aristotle’s philosophy is not in every respect clearly worked out. In fact there are two Aristotles, the one being a Platonist, the other a naturalist, the one believing in universals, the other investigating concrete things and taking individuals as real beings. But both Aristotles and with them both parties of the schoolmen had no clear conception of the nature of ideas, what they are, and what they purport, and how we can discriminate between their subjective and objective elements. Ideas have a meaning. Is their meaning purely mental or has it an objective value? We say that it has.