He could distinguish internal objects from external ones, and among external objects those with selves from those without. These distinctions were easily made and the margins of error were small but not vanishing. For each object there was a part believed to be intrinsic to it and the remainder was taken to be blended with qualities derived from himself. These qualities could be varied either by will or by way of changes that also affected strictly internal objects. The variations in objects consistent with variations in himself were brought together in the notion of a perspective. Other kinds of variations which included those external objects with selves suggested that perspectives had an objective existence, and that this was the definitive characteristic of all selves. This understanding opened strange abysses in his world, prior to it his sense of other selves was of an implicit intimacy, it consisted in his feeling into them as if they were the same.