Just as no event and no form completely resembles one another, neither does any completely differ. What an ingenious medley is Nature’s: if our faces were not alike we could not tell man from beast: if they were not unalike we could not tell man from man. All things are connected by some similarity; yet every example limps and any correspondence which we draw from experience is always feeble and imperfect; we can nevertheless find some corner or other by which to link our comparisons.
~ Montaigne, The Complete Essays (1587-88)