The concept of a crack-stability map is developed by considering the interaction between the crack-driving force and the rising crack-growth resistance of a toughened ceramic. The map plots normalized transition crack length as function of the ratio of the crack-initiation fracture toughness and the plateau toughness to delineate regimes of stable and unstable crack growth. The plot is used to analyze R curves and fracture stresses of a transformation-toughened Ce-TZP/Al2O3. It is shown that the fracture stress and the small scatter measured for this ceramic are consistent with its R-curve behavior, which enables stable growth of surface cracks from flaws (pores and second-phase particles), leading to a flaw-insensitive ceramic.