BOOK I.
DOUBT.
I believe that I am now tolerably well acquainted with no inconsiderable part of the world that surrounds me, and I have certainly employed sufficient labour and care in the acquisition of this knowledge. I have put faith only in the concurrent testimony of my senses, only in repeated and unvarying experience;—what I have beheld, I have touched—what I have touched, I have analyzed;—I have repeated my observations again and again; I have compared the various phenomena with each other; and only when I could understand their mutual connexion, when I could explain and deduce the one from the other, and calculate the result beforehand, and the examination of the result had proved the accuracy of my calculations, have I been satisfied. Therefore I am now as well assured of the accuracy of this part of my knowledge, as of my own existence; I walk with a firm step in these understood spheres of my world, and do actually every moment venture welfare and life itself on the certainty of my convictions.
But—what am I myself, and what is my vocation?
