George MacDonald

I'm enjoying trying to decipher some of George MacDonald's sonnets in his book Diary of an Old Soul. These beauties take some serious thought on my part. Even then I don't always understand exactly what they mean. It's fun to try and figure them out, though. Here's the last one I read:

Thy will is truth - 'tis therefore fate, the strong.
Would that my will did sweep full swing with thine!
Then harmony with every spheric song,
And conscious power, would give sureness divine.
Who thinks to thread they great laws' onward throng,
Is as a fly that creeps his foolish way
Athwart an engine's wheels in smooth resistless play.

Here's my best guess so far:
God's will is what is right and is destined to happen and is stronger than wrong
he wishes that he could keep his will aligned with God's
then he would be in harmony with the earth's song (because the earth is within God's will?)
Knowing that he is within God's will would give him the power of knowing he was doing what was divinely right

However, A person who thinks that God's will can be easily tied in a straight line
is trying foolishly to tie something up that can not be tied (? Very iffy on this last part.)

Any thoughts?