  It is widely believed that quadratic divergences severely restrict natural
constructions of particle physics models beyond the standard model (SM).
Supersymmetry provides a beautiful solution, but the recent LHC experiments
have excluded large parameter regions of supersymmetric extensions of the SM.
It will now be important to reconsider whether we have been misinterpreting the
quadratic divergences in field theories. In this paper, we revisit the problem
from the viewpoint of the Wilsonian renormalization group and argue that
quadratic divergences, which can always be absorbed into a position of the
critical surface, should be simply subtracted in model constructions. Such a
picture gives another justification to the argument that the scale invariance
of the SM, except for the soft-breaking terms, is an alternative solution to
the naturalness problem. It also largely broadens possibilities of model
constructions beyond the SM since we just need to take care of logarithmic
divergences, which cause mixings of various physical scales and runnings of
couplings.
