The World as Will and Idea

I propose to point out here how this book must be read in order to be thoroughly understood. By means of it I only intend to impart a single thought. Yet, notwithstanding all my endeavours, I could find no shorter way of imparting it than this whole book. I hold this thought to be that which has very long been sought for under the name of philosophy, and the discovery of which is therefore regarded by those who are familiar with history as quite as impossible as the discovery of the philosopher's stone, although it was already said by Pliny: Quam multa fieri non posse, priusquam sint facta, judicantur? (Hist. nat. 7, 1.)
According as we consider the different aspects of this one thought which I am about to impart, it exhibits itself as that which we call metaphysics, that which we call ethics, and that which we call æsthetics; and certainly it must be all this if it is what I have already acknowledged I take it to be.