(2) We must, nevertheless, not cease to strive towards the perfection unattainable on earth, but which shall be attained hereafter.

Our destiny, the God within us, demands that.

And we lose it, if we are content with our earthly life, even with its highest things, with knowledge, beauty, or with love.
Hence, the foundation of Browning's theory is a kind of Original Sin in us, a natural defectiveness deliberately imposed on us by God, which prevents us attaining any absolute success on earth.

And this defectiveness of nature is met by the truth, which, while we aspire, we know--that God will fulfil all noble desire in a life to come.
We must aspire then, but at the same time all aspiring is to be conterminous with steady work within our limits.

Aspiration to the perfect is not to make us idle, indifferent to the present, but to drive us on.