"I have a great deal of what the world calls courage, but I have no prudence."

"Invisible things are the only realities."

"In one case out of a hundred a point is excessively discussed because it is obscure; in the ninety-nine remaining it is obscure because it is excessively discussed."

"The truth is, I am heartily sick of this life & of the nineteenth century in general. (I am convinced that every thing is going wrong)."

"If you determine to abandon me — here take I my farewell — Neglected — I will be doubly ambitious, & the world shall hear of the son whom you have thought unworthy of your notice."