  We consider a field theoretical model where a SU(2) fermion doublet,
subjected to non-Abelian gauge interactions, is also coupled to a complex
scalar field doublet via a Yukawa and an irrelevant Wilson-like term. Despite
the presence of these two chiral breaking operators in the Lagrangian, an exact
symmetry acting on fermions and scalars prevents perturbative mass corrections.
In the phase where fermions are massless (Wigner phase) the Yukawa coupling can
be tuned to a critical value at which chiral transformations acting on fermions
only become a symmetry of the theory (up to cutoff effects). In the
Nambu-Goldstone phase of the critical theory a fermion mass term of dynamical
origin is expected to arise in the Ward identities of the purely fermionic
chiral transformations. Such a non-perturbative mechanism of dynamical mass
generation can provide a "natural" (\`a la 't Hooft) alternative to the Higgs
mechanism adopted in the Standard Model. Here we lay down the theoretical
framework necessary to demonstrate the existence of this mechanism by means of
lattice simulations.
