In considering the difference between consolidation and restoration, it should be specified which among old buildings must be subjected to restoration. With reference to such a specific question, considerations regarding the philosophy of safety and the determination of the threshold of acceptable risk are developed. Taking into account the available techniques of consolidation and the factors that determine the costs of interventions in stability, some observations on the possible methods of examination suited for evaluating the possibility and the convenience of accomplishing structural restoration, are developed; the practical consequences of the lack of a general theory on masonry structures are also given. It is concluded that the restoration of a monument's masonry structures: 1) excludes a resort to technical, scientific methods and criteria, identically applicable in every case; on the contrary, it requires a specific study of the monument in question, in order to determine the methods applicable to it; 2) is based on the historical research that tends to define, for a particular monument under examination, the previously applied techniques, the events regarding the original structure and the events the monument has successively suffered (transformation, damages, restorations, etc.); 3) is based on a previous determination of the level of safety to which the building has to be brought after restoration; 4) is conditioned by the necessity to assure at the same time the protection of the cultural asset and of individuals; 5) is conditioned by the necessity to satisfy the theoretical principles of the conservation of the architectural heritage (and, in particular, the historical and aesthetical requirements); 6) is conditioned by the necessity of resorting to interventions which involve works of simple execution and low costs.