Why be Natural?

Naturalness, as a guiding principle for effective field theories (EFTs), requires that there be no sensitive correlations between phenomena at low- and high-energy scales. This essay considers four reasons to adopt this principle: (i) natural EFTs exhibit modest empirical success; (ii) unnatural EFTs are improbable; (iii) naturalness underwrites what Williams (Stud Hist Philos Mod Phys 51:82, 2015) calls a “central dogma” of EFTs; namely, that phenomena at widely separated scales should decouple; and (iv) naturalness underwrites a non-trivial notion of emergence. I argue that the first three are not compelling reasons, whereas the fourth is.