Henry David Thoreau:
To affect the quality of the day, that is the highest of arts.
What is the structure of this sentence?
I think it's safe to simplify to "To do, that is A".
Is it a cleft sentence? Is it an inversion?
Can I change "that" to "this", or "it"?
Would the normal order be "A is to do"?
Edit:
My question focus on an infinitive before the main clause, and the subject of the main clause is "that".
I also found "to be or not to be, that is the question". This quote so happens to also use "that"? Are there any hidden rules?