The actual correlation then is between simple, i.e. not further analysable, psychical content and complex physical processes. If, however, in contradiction to this, we introduce the metaphysical postulate of a correspondence between the psychically simple and the physically simple, we are inclined to go further and to presuppose a continuous correspondence between the two series of phenomena right up to the highest and most complicated content of consciousness. This regular relation between psychical elements and physical processes then becomes changed into a metaphysical parallelism, in which in content as well as in form the psychical becomes a copy of the physical, and the physical a copy of the psychical phenomenon. This hypothesis finds expression in the words of Spinoza, "The order and combination of ideas is the same as the order and combination of things." Such an idea was thinkable as long as the physical side of the qualities of living beings was so little known, and as long as there was no explanation of those psychological principles, which control the combination of processes of consciousness from simple sense-perceptions to complex thought-processes. At that Lime philosophy could take the liberty of building up reality out of abstract ideas, such as substance and causality. At the present day metaphysics, if it wishes to make any claim to respect, must build upon the real facts and not upon those ideas used from purely logical, dialectical motives. Even from this point of view there remains a "principle of psychological parallelism" in the sense that there is no psychical process, from the simplest sensation and affective elements to the most complex thought-processes, which does not run parallel with a physical process. Now sensation and affective elements cannot be compared in that way, since a simple process in the one case does not correspond to even a relatively simple one in the other, and this of course is valid for all other contents of consciousness formed from these elements. We meet everywhere physical and psychical as incomparable qualities of the united psycho-physical individual, and each of these must be judged according to the laws of combinations of elements, which are expressed in the combination itself. Since these qualities themselves are disparate, it can therefore never happen that the two principles come into antagonism with each other, whereas on the other hand, if we try to transfer the conditions that are only valid for the one side of the phenomena of life to the other side, we will very soon either come into antagonism with facts, or be forced to abandon an interpretation of a part of life placed in this manner under a strange point of view. Thus from the present-day psychological standpoint, which must be authoritative for a philosophical consideration, we can only speak of a "parallelism" between psychical and physical in as far as all elements of psychical life are joined to physical processes.