Interpersonal knowledge is unique-yet it can legitimately be called knowledge. The ideal of the objective unity of knowledge can be illustrated only in one way-by analogy drawn from a closed system of knowledge, for example the abstract construction of mathematics. It is in philosophy in the traditional sense that we can find a good illustration, on the one hand of the ideal of the objective unity of knowledge, and on the other hand of the impossibility of moving more than a very short distance towards the ideal of unity. Art, religion, morality, our knowledge of persons, obviously start from our entanglement with things, though in different ways. The situation of sense-perception is quite different from the situation of discursive thinking: the relationship of the scientist to his object is very different from that of the listener to music, whilst in the knowledge of persons it is sometimes entirely inappropriate to speak of the knowledge of an 'object' at all.