In his letter “But what is physics?” (Physics Today, April 2021, page 12), Peter Zimmerman raises an interesting question about physics and physicists. He recalls the definition given by his former professor Leonard Schiff: “Physics is whatever physicists do.”
Schiff’s definition, however, seems like a tautology. I prefer one given by Gabriel Weinreich:
Physics is delineated, not by its subject matter, but by the methods of thought that a physicist uses.1
Additionally, in their December 1995 article in Physics Today (page 25), Sol Gruner, James Langer, Phil Nelson, and Viola Vogel provide a definition of physicist that I still treasure:
The physicist is most cogently identified, not by the subject studied, but by the way in which a subject is studied and by the nature of the information being sought.
Both definitions point to the methods involved.
