There was no other way to develop the manifold aptitudes of man than to bring them in opposition with one another.  This antagonism of forces is the great instrument of culture, but it is only an instrument; for as long as this antagonism lasts, man is only on the road to culture.  It is only because these special forces are isolated in man, and because they take on themselves to impose an exclusive legislation, that they enter into strife with the truth of things, and oblige common sense, which generally adheres imperturbably to external phaenomena, to dive into the essence of things.  While pure understanding usurps authority in the world of sense, and empiricism attempts to subject this intellect to the conditions of experience, these two rival directions arrive at the highest possible development, and exhaust the whole extent of their sphere.  While on the one hand imagination, by its tyranny, ventures to destroy the order of the world, it forces reason, on the other side, to rise up to the supreme sources of knowledge, and to invoke against this predominance of fancy the help of the law of necessity.

By an exclusive spirit in the case of his faculties, the individual is fatally led to error; but the species is led to truth.  It is only by gathering up all the energy of our mind in a single focus, and concentrating a single force in our being, that we give in some sort wings to this isolated force, and that we draw it on artificially far beyond the limits that nature seems to have imposed upon it.  If it be certain that all human individuals taken together would never have arrived, with the visual power given them by nature, to see a satellite of Jupiter, discovered by the telescope of the astronomer, it is just as well established that never would the human understanding have produced the analysis of the infinite, or the critique of pure reason, if in particular branches, destined for this mission, reason had not applied itself to special researches, and if, after having, as it were, freed itself from all matter, it had not by the most powerful abstraction given to the spiritual eye of man the force necessary, in order to look into the absolute.  But the question is, if a spirit thus absorbed in pure reason and intuition will be able to emancipate itself from the rigorous fetters of logic, to take the free action of poetry, and seize the individuality of things with a faithful and chaste sense?  Here nature imposes even on the most universal genius a limit it cannot pass, and truth will make martyrs as long as philosophy will be reduced to make its principal occupation the search for arms against errors.