I would certainly make it against law, as it plainly is against nature, for cousins-german to marry; and if we could pair ourselves as we pair our live stock, and give ear to the teaching of an enlightened zoönomy, we might soon drive many of our fellest diseases out of our breed; but the law of personality, of ultroneousness, of free will, that which in a great measure makes us what we are, steps in and forbids anything but the convincement and force of reason.
Source: wiktionary