With all your science – can you tell how it is, and whence it is, that light comes into the soul? – Henry David Thoreau

There are relapses in the disorders of the soul as well as in those of the body. What we take to be our cure is most often nothing but an intermission or a change of the disorder. – François VI de la Rochefoucault (1613–1680)

The souls impurity consists in bad judgments, and purification consists in producing in it right judgments, and the pure soul is one which has right judgments. – Epictetus