What are the general rules on deciding between il and ce for referring to an idea in the form of a proposition or other gender-less form (such as an infinitive)?
Examples in English would include:
(a) Is he? That is the question.
(b) Is he? It's hard to tell.
(c) It's hard to know what to think.
What I intended was that in (a) and (b) the pronoun should follow the idea it refers to, but in (c) precede. In (a) the idea is assigned to a class, but in (b) only described. Maybe in (c), the pronoun is expletive and does not refer at all.
Whenever I could use either ce or il please tell me so and what the difference may be. If some third pronoun works better or as well, please also tell me.
This request may be rather indefinite, but if I am obviously overlooking some important factor affecting the choice please let me know using example sentences. Thank you.