  We introduce a "radial" two-point invariant for quantum field theory in de
Sitter (dS) analogous to the radial coordinate used in conformal field theory.
We show that the two-point function of a free massive scalar in the
Bunch-Davies vacuum has an exponentially convergent series expansion in this
variable with positive coefficients only. Assuming a convergent
K\"all\'en-Lehmann decomposition, this result is then generalized to the
two-point function of any scalar operator non-perturbatively. A corollary of
this result is that, starting from two-point functions on the sphere, an
analytic continuation to an extended complex domain is admissible. dS two-point
configurations live inside or on the boundary of this domain, and all the paths
traced by Wick rotations between dS and the sphere or between dS and Euclidean
Anti-de Sitter are also contained within this domain.
