What is the main belief which Darwin is arguing against throughout the book?

Is Darwin being intellectually honest by explicitly leaving out the factual basis he believes is necessary to prove his theory and asking the reader to trust that he has researched the topic thoroughly? How does his promise to publish a future work with this data affect this?

Why does Darwin devote the majority of the book to answering objections rather than providing evidence for this theory?

When responding to objections based on the geological record, Darwin responds by saying that the geological record is imperfect and incomplete. However, in the following chapter, he uses evidence from the geological record to support his theory. Is he contradicting himself by doing this?

At several points in the book, Darwin raises an objection and admits that he cannot provide a definitive response to it...