What hidden mystery in this riddle lies?

MEPHISTOPHELES

The spirit I, which evermore denies!
And justly; for whate'er to light is brought
Deserves again to be reduced to naught;
Then better 'twere that naught should be.
Thus all the elements which ye
Destruction, Sin, or briefly, Evil, name,
As my peculiar element I claim.

FAUST

Thou nam'st thyself a part, and yet a whole I see.

MEPHISTOPHELES

The modest truth I speak to thee.
Though folly's microcosm, man, it seems,
Himself to be a perfect whole esteems:
Part of the part am I, which at the first was all,
A part of darkness, which gave birth to light,
Proud light, who now his mother would enthrall,
Contesting space and ancient rank with night.
Yet he succeedeth not, for struggle as he will,
To forms material he adhereth still;
From them he streameth, them he maketh fair,
And still the progress of his beams they check;
And so, I trust, when comes the final wreck,