Again, nature is the superficies of the soul. It is the part that comes in contact with the world of things and people. A man's nature is what he is for other people; what he is in and for himself alone is personality. There is a substance or self-existence of the psychic states. Thought, will and feeling have all and each an external reference. The internal reference of the whole is the core of being. Our perception of personality in other people is a subtle thing. In the ordinary give and take of life we are not aware of it. It is when we realise the subject as a self-existent unity that we recognise personality. We judge a man's nature by his thought or will or feelings as conveyed through the ordinary channels of communication. Personality is felt. It is a magnetism that influences, but remains inarticulate. Person and nature differ also in respect of relation to the body. The co-existence of heterogeneous natures in the same body is a fact of experience. Different universes of thought, different levels of will and feeling can be lodged in one organism. The higher the development of the individual, the more clearly marked is the duality or plurality of nature. It is otherwise with personality. In normal cases no two personalities can tenant the one body. The unity of the organism is the outward expression and guarantee of the unity of the person. There are of course pathological cases which form exceptions to this rule. Such cases, however, only serve to emphasise the distinction between person and nature. In cases of dual personality the occupancy of the one body is not simultaneous. Jekyll alternates with Hyde. Dual personality is a totally different phenomenon from duality of nature. Duality of nature is relatively superficial. In dual personality the divergence in mental and moral outlook is so radical that responsibility for the acts of the one entity cannot attach to the other entity.