The fact that we are incapable of the synoptic perspective. When man views a given object in different respects, he is focusing on different aspects of that object, and in virtue of this fact, some relations will be internal to the context of his inquiry, and others will be external. It is proper to recognize that these aspects of the object exist independently of man. However, one must also recognize that, metaphysically, these aspects are inseparable aspects of the object. When we find it necessary to view an object in a certain respect, but not in others, it is only because we are unable to grasp the whole of existence in all its particularity.
Human consciousness is of a specific nature.
Consequently, human consciousness is limited, and thus incapable of achieving the synoptic viewpoint. The dichotomy is a product of our recognition of man's need for unit-economy. Man cannot grasp all of existence in all of its particularity in a single act of cognition. In order to perform any cognition at all at any given time, and do so systematically, he must reduce the number of units which he is dealing with to a manageable level. He must narrow his focus, isolating a context in which cognition is to be performed by regarding some components as internal to that context, and regarding other components as external to that context.