One should not be deceived: great spirits are skeptics ... Strength, FREEDOM which is born of the strength and overstrength of the spirit, proves itself by skepticism. Men of conviction are not worthy of the least consideration in fundamental questions of value and disvalue. Convictions are prisons.
What the sense feeleth, what the spirit discerneth, hath never its end in itself. But sense and spirit would fain persuade thee that they are the end of all things: so vain are they.
One must never have spared oneself, one must have acquired hardness as a habit to be cheerful and in good spirits in the midst of nothing but hard truths.