I don't find it that tricky, intelligence does come from the brain.

> That's like equating the workings of my bicycle to my decision to ride to a particular place

Both one's brain and one's "intelligence" belong to the same person, like, physically and materially, which is not true when it comes to your bicycle example. More to the point, I find the comparison itself kind of self-describing, it's like deciding to "outsource" intelligence to some other external, non-ethereal entity (like a bicicle that is physically separate from a human being) in order to avoid those hard questions the OP was alluding to (hard questions that oftentimes also involve the political side of things).