  My aim in this paper is twofold: (i) to distinguish two notions of
naturalness employed in BSM physics and (ii) to argue that recognizing this
distinction has methodological consequences. One notion of naturalness is an
"autonomy of scales" requirement: it prohibits sensitive dependence of an
effective field theory's low-energy observables on precise specification of the
theory's description of cutoff-scale physics. I will argue that considerations
from the general structure of effective field theory provide justification for
the role this notion of naturalness has played in BSM model construction. A
second, distinct notion construes naturalness as a statistical principle
requiring that the values of the parameters in an effective field theory be
"likely" given some appropriately chosen measure on some appropriately
circumscribed space of models. I argue that these two notions are historically
and conceptually related but are motivated by distinct theoretical
considerations and admit of distinct kinds of solution.
