If two or more instances of the phenomenon under investigation have only one circumstance in common, the circumstance in which alone all the instances agree is the cause (or effect) of the given phenomenon.

Stupidity is much the same all the world over. A stupid person's notions and feelings may confidently be inferred from those which prevail in the circle by which the person is surrounded. Not so with those whose opinions and feelings are an emanation from their own nature and faculties.

The moment one asks himself whether he is happy, he ceases to be so.

No one can be a great thinker who does not recognize that as a thinker it is his first duty to follow his intellect to whatever conclusions it may lead.

I know tolerably well what Ireland was, but have a very imperfect idea of what Ireland is.

The worth of the state, in the long run, is the worth of the individuals composing it.

Money is a machine for doing quickly and commodiously what would be done, though less quickly and commodiously, without it.