The theoretical physicist Steven Weinberg joins a list of distinguished scientists who have turned their hands to historical or philosophical reflections on science. Mr. Weinberg won his Nobel Prize in physics in 1979 for theoretical work on the unification of forces operating between subatomic particles. As his active involvement in research declined, he has become a prolific contributor to what’s called the “public understanding of science”—writing a popular tract on the search for a “Final Theory” in physics, decrying the corrosive effects of religion on knowledge and morality, trying to protect spending on particle...