Now 'why a thing is itself' is doubtless a meaningless inquiry; for the fact or the existence of the thing must already be evident (e.g. that the moon is eclipsed), but the fact that a thing is itself is the single formula and the single cause to all such questions as why the man is man, or the musical musical, unless one were to say that each thing is inseparable from itself; and its being one just meant this.