The simplest known complete representation of my utility function is my brain, combined with some supporting infrastructure and a question-asking procedure. Any utility function that is substantially simpler than my brain has almost certainly left something out.

The first step in extracting a human's volition is to develop a complete understanding of the brain, including the ability to simulate it. We are currently stuck there. We have some high-level approximations that work around needing this understanding, but their accuracy is questionable.