In the Grotto of Pausilippo, darkness continues to augment as we advance towards the interior; but when once we have passed the middle, day-light again appears at the other end and shows us the way; so also in this case: just at the point where the outwardly directed light of the understanding with its form of causality, gradually yielding to increasing darkness, had been reduced to a feeble, flickering glimmer, behold! we are met by a totally different light proceeding from quite another quarter, from our own inner self, through the chance circumstance, that we, the judges, happen here to be the very objects that are to be judged. The growing difficulty of the comprehension of the causal nexus, at first so clear, had now become so great for perception and for the understanding--the agent in it--that, in animal actions, the very existence of that nexus seemed almost doubtful and those actions appeared to be a sort of miracle. But, just at this point, the observer receives from his own inner self the direct information that the agent in them is the will--that very will, which he knows better and more intimately than anything that external perception can ever supply. This knowledge alone must be the philosopher's key to an insight into the heart of all those processes in unconscious Nature, concerning which causal explanation--although, here, to be sure, more satisfactory than in the processes last considered, and the clearer, the farther those processes were removed from these--nevertheless had still left an unknown _x_, and could never quite illumine the inside of the process, even in a body propelled by impact or attracted by gravity. This _x_ had continued expanding till finally, on the highest degrees of the scale, it had wholly repelled causal explanation. But then, just when the power of causal explanation had been reduced to a minimum, that _x_ revealed itself as _the will_--reminding us of Mephistopheles when, yielding to Faust's learned exorcisms, he steps forth out of the huge grown poodle whose kernel he was. In consequence of the considerations I have here set forth at length, we can surely hardly avoid recognising _the identity of this x_, even on the lowest degrees of the scale, where it was but faintly perceptible; then higher up, where it extended its obscurity more and more; and finally on the highest degrees, where it cast a shadow upon all things--till, at the very top, it reveals itself to our consciousness in our own phenomenal being, as _the will_. The two primarily different sources of our knowledge, that is to say the inward and the outward source, have to be connected together at this point by reflection. It is quite exclusively out of this connection that our comprehension of Nature, and of our own selves arises; but then the inner side of Nature is disclosed to our intellect, which by itself alone can never reach further than to the mere outside; and the mystery which philosophy has so long tried to solve, lies