been written since Kant. Another indirect proof of the same doctrine, though in the way of error, is afforded by the French sensational philosophers, who, since Condillac trod in the footsteps of Locke, have laboured to show once for all that the whole of our perception and thinking can be referred to mere sensations (penser c'est sentir), which, after Locke's example, they call idées simples, and through the mere coming together and comparison of which the whole objective world is supposed to build itself up in our heads. These gentlemen certainly have des idées bien simples. It is amusing to see how, lacking alike the profundity of the German and the honesty of the English philosopher, they turn the poor material of sensation this way and that way, and try to increase its importance, in order to construct out of it the deeply significant phenomena of the world of perception and thought. But the man constructed by them would necessarily be an Anencephalus, a Tête de crapaud, with only organs of sense and without a brain. To take only a couple of the better attempts of this sort out of a multitude of others, I may mention as examples Condorcet at the beginning of his book, "Des Progrès de l'Esprit Humain," and Tourtual on Sight, in the second volume of the "Scriptores Ophthalmologici Minores," edidit Justus Radius (1828).
The feeling of the insufficiency of a purely sensationalistic explanation of perception is in like manner shown in the assertion which was made shortly before the appearance of the Kantian philosophy, that we not only have ideas of things called forth by sensation, but apprehend the things themselves directly, although they lie outside us – which is certainly inconceivable. And this was not meant in some idealistic sense, but was said from the point of view of common realism. This assertion is well and pointedly put by the celebrated Euler in his "Letters to a German Princess," vol. ii. p. 68. He says: "I therefore believe that the sensations (of the senses) contain something more than philosophers imagine. They are not
