The relation of these different systems to each other is thus already intimated. The historical and collective life of the race is bound together by the idea of a spiritual and intellectual progress, and manifests a regular order of advancing, though not always continuous, stages of development. In this, the fact harmonizes with what we should expect from antecedent probabilities. Since, therefore, every philosophical system is only the philosophical expression of the collective life of its time, it follows that these different systems which have appeared in history will disclose one organic movement and form together one rational and internally connected (_gegliedertes_) system. In all their developments, we shall find one constant order, grounded in the striving of the spirit ever to raise itself to a higher point of consciousness and knowledge, and to recognize the whole spiritual and natural universe, more and more, as its outward being, as its reality, as the mirror of itself.
_Hegel_ was the first to utter these thoughts and to consider the history of philosophy as a united process, but this view, which is, in its principle, true, he has applied in a way which would destroy the freedom of human actions, and remove the very conception of contingency, _i. e._ that any thing should be contrary to reason. Hegel’s view is, that the succession of the systems of philosophy which have appeared in history, corresponds to the succession of logical categories in a system of logic. According to him, if, from the fundamental conceptions of these different philosophical systems, we remove that which pertains to their outward form or particular application, &c., so do we find the different steps of the logical conceptions (_e. g._ being, becoming, existence, being _per se_ (_fürsichseyn_) quantity, &c.). And on the other hand, if we take up the logical process by itself, we find also in it the actual historical process.
This opinion, however, can be sustained neither in its principle nor in its historical application. It is defective in its principle, because in history freedom and necessity interpenetrate, and, therefore, while we find, if we consider it in its general aspects, a rational connection running through the whole, we also see, if we look solely at its individual parts, only a play of numberless contingencies, just as the kingdom of nature, taken as a whole, reveals a rational plan in its successions, but viewed only in its parts, mocks at every attempt to reduce them to a preconceived plan. In history we have to do with free subjectivities, with individuals capable of originating actions, and have, therefore, a factor which does not admit of a previous calculation. For however accurately we may estimate the controlling conditions which may attach to an individual, from the general circumstances in which he may be placed, his age, his associations, his nationality, &c., a free will can never be calculated like a mathematical problem. History is no example for a strict arithmetical calculation. The history of philosophy, therefore, cannot admit of an apriori construction; the actual occurrences should not be joined together as illustrative of a preconceived plan; but the facts, so far as they can be admitted, after a critical sifting, should be received as such, and their rational connection be analytically determined. The speculative idea can only supply the law for the arrangement and scientific connection of that which may be historically furnished.