proposition, Leibnitz defends the first by a delicate application of the concept of unconscious representation and of implicit knowledge, which his predecessor rejects out of hand. [Footnote 1: According to Fox Bourne this first book was written after the others. Geil _(Ueber die Abhängigkeit Lockes von Descartes_, Strassburg, 1887, chap, iii.) has endeavored to prove that, since the arguments controverted are wanting in Descartes, the attack was not aimed at Descartes and his school, but at native defenders of innate ideas, as Lord Herbert of Cherbury and the English Platonists (Cudworth, More, Parker, Gale). That along with these the Cartesian doctrine was a second and chief object of attack is shown by Benno Erdmann in his discussion of the treatises by G. Geil and R. Sommer _(Lockes Verhältnis zu Descartes_, Berlin, 1887) in the _Archiv für Geschichte der Philosophie_, ii, pp. 99-121.] Locke's positive answer to the question concerning the origin of ideas is given in his second book. Ideas are not present in the understanding from the beginning, nor are they originated by the understanding, but received through sensation. The understanding is like a piece of white paper on which perception inscribes its characters. All knowledge arises in experience. This is of two kinds, derived either from the external senses or the internal sense. The perception of external objects is termed Sensation, that of internal phenomena (of the states of the mind itself) Reflection. External and internal perception are the only windows through which the light of ideas penetrates into the dark chamber of the understanding. The two are not opened simultaneously, however, but one after the other; since the perceptions of the sensible qualities of bodies, unlike that of the operations of the mind itself, do not require an effort of attention, they are the earlier. The child receives ideas of sensation before those of reflection; internal perception presupposes external perception. In this distinction between sensation and reflection, we may recognize an after-effect of the Cartesian dualism between matter and spirit. The antithesis of substances has become a duality in the faculties of perception. But while Descartes had so far forth ascribed precedence to the mind in that he held the self-certitude of the ego to be the highest and clearest of all truths and the soul to be better known than the body, in Locke the relation of the two was reversed, since he made the perception of self dependent on the precedent perception of external objects. This antithesis was made still sharper in later thinking, when Condillac made full use of the priority of sensation, which in Locke had remained without much effect; while Berkeley, on the other hand, reduced external perception to internal perception.