  The quantum of action $\hbar$, multiplying in certain powers perturbative
vertices in 4D gauge theory, is related to the action of just-not-resolved
selfdual and thermal gauge field configurations, calorons and anticalorons, of
charge modulus unity. Appealing to the derivation of the effective theory for
the deconfining phase of SU(2) Yang-Mills thermodynamics, we conclude that
these vertex inducers convey a rapidly decreasing interaction strength between
{\sl fundamental} plane waves when the momentum transfer is increased away from
the scale of maximal, {\sl effective} resolution. This adds a deeper
justification to the renormalization programme of perturbation theory which
ignores the contribution to the partition function of nontrivially selfdual
configurations. We also point out a connection between the QED fine-structure
constant $\alpha$ and the electric-magnetically dual of the effective gauge
coupling in the deconfining phase, and we illustrate the workings of effective
loops in the expansion of the pressure.
