  We argue that deriving an effective field theory from string theory requires
a Wilsonian perspective with a physical cutoff. Employing proper time
regularization we demonstrate the decoupling of states and contrast this with
what happens in dimensional regularization. In particular we point out that
even if the cosmological constant (CC) calculated from some classical action at
some ultra-violet scale is negative, this does not necessarily imply that the
CC calculated at cosmological scales is also negative, and discuss the possible
criteria for achieving a positive CC starting with a CC at the string/KK scale
which is negative. Obviously this has implications for swampland claims.
