to mind that all this is first of all merely a phenomenon of the brain, and is affected with such great, so many, and such different subjective conditions that its supposed absolute reality vanishes away, and leaves room for an entirely different scheme of the world, which consists of what lies at the foundation of that phenomenon, i.e., what is related to it as the thing in itself is related to its mere manifestation.
"The world is my idea" is, like the axioms of Euclid, a proposition which every one must recognise as true as soon as he understands it; although it is not a proposition which every one understands as soon as he hears it. To have brought this proposition to clear consciousness, and in it the problem of the relation of the ideal and the real, i.e., of the world in the head to the world outside the head, together with the problem of moral freedom, is the distinctive feature of modern philosophy. For it was only after men had spent their labour for thousands of years upon a mere philosophy of the object that they discovered that among the many things that make the world so obscure and doubtful the first and chiefest is this, that however immeasurable and massive it may be, its existence yet hangs by a single thread; and this is the actual consciousness in which it exists. This condition, to which the existence of the world is irrevocably subject, marks it, in spite of all empirical reality, with the stamp of ideality, and therefore of mere phenomenal appearance. Thus on one side at least the world must be recognised as akin to dreams, and indeed to be classified along with them. For the same function of the brain which, during sleep, conjures up before us a completely objective, perceptible, and even palpable world must have just as large a share in the presentation of the objective world of waking life. Both worlds, although different as regards their matter, are yet clearly moulded in the one form. This form is the intellect, the function of the brain. Descartes was probably the first who attained to the
