Abstract

Naturalness, as a guiding principle for effective field theories, requires that there be no sensitive correlations between phenomena at low- and high-energy scales. This essay considers four reasons to adopt this principle: natural EFTs exhibit modest empirical success; unnatural EFTs are improbable; naturalness underwrites what Williams calls a “central dogma” of EFTs; namely, that phenomena at widely separated scales should decouple; and naturalness underwrites a non-trivial notion of emergence. I argue that the first three are not compelling reasons, whereas the fourth is.