C. Bagnuls*, C. Bervillier**
*Service de Physique de l'Etat Condens\'{e}e,
**Service de Physique Th\'{e}orique
C. E. A.-Saclay, F91191 Gif-sur-Yvette Cedex, France
We shortly illustrate how the field--theoretic approach to critical phenomena takes place in the more complete Wilson theory of renormalization and qualitatively discuss its domain of validity. By the way, we suggest that the differential renormalization functions (like the $\beta $-function) of the perturbative scalar theory in four dimensions ($\varphi _{4}^{4}$) should be Borel summable provided they are calculated within a minimal subtraction scheme.