User blog comment:Ygrain/EDI and the geth: their purpose in the story?/@comment-24174486-20120723182551/@comment-3581090-20120726203415

I think Ygrain's hit the nail on the head with her assessment above (both in this and in another of the comment strands): per basic narrative structure, the placement of the reveal about the Catalyst's motivation at the climax of the story implies its central significance to the plot--including all of its inherent

Also, I believe the Crucible is what opens the Catalyst's mind to the three new solutions, not Shepard. While he acknowledges that Shepard's presence proves that his Reaper solution no longer works, the Catalyst says that the Crucible "changed" him.