An incremental description of (linear elastic) fracture mechanics is presented which shows a perfect analogy with the plasticity theory. After comparing (in terms of angle of propagation, of safe-equilibrium domains, and of energy dissipation) several criteria for crack propagation, the formulation of a generic criterion stemming from the associated plasticity theory is presented and its feature discussed. The analogy between plasticity and quasi-static crack growth leads also to a new algorithm for crack propagation for an arbitrary number of cracks in multi-connected materials, which is driven by the increment of external actions. Stability of crack path under mode I loading is finally analyzed.