Now that the election is over, libertarians can counsel the new president on positions and policies that they believe will create a better world. I doubt very much that counseling Hillary Clinton would have been a fruitful project had she been elected, but Donald Trump is a very different story. He has yet to translate his creative impulses and politics into hardened doctrines and policies. A useful political approach is to articulate general positions that have sound fundamentals and then to derive practical policies from them. They won’t please everyone and they will be imperfect. The...