To answer any one question, you find you must answer another; and to answer that you must answer a third, and then a fourth; and so on for ever and ever.
For ever and ever?
Of course.

If we thought and searched over the Universe--ay, I believe, only over this one little planet called earth--for millions on millions of years, we should not get to the end of our searching.

The more we learnt, the more we should find there was left to learn.

All things, we should find, are constituted according to a Divine and Wonderful Order, which links each thing to every other thing; so that we cannot fully comprehend any one thing without comprehending all things: and who can do that, save He who made all things?
Therefore our true wisdom is never to fancy that we do comprehend: never to make systems and theories of the Universe (as they are called) as if we had stood by and looked on when time and space began to be; but to remember that those who say they understand, show, simply by so saying, that they understand nothing at all; that those who say they see, are sure to be blind; while those who confess that they are blind, are sure some day to see.

All we can do is, to keep up the childlike heart, humble and teachable, though we grew as wise as Newton or as Humboldt; and to follow, as good Socrates bids us, Reason whithersoever it leads us, sure that it will never lead us wrong, unless we have darkened it by hasty and conceited fancies of our own, and so have become like those foolish men of old, of whom it was said that the very light within them was darkness.