The problem can be illustrated by contemplating an ostensible impossibility: for several countries a defensible measure of the extent and efficacy of control attempts in general and a corresponding measure for each of the several basic types. The moon landing required efficacious inanimate control on a massive scale; but it was realized by a nation in which annually there are millions of violent crimes, each representing a failure in attempted behavior control. Punishment is a subclass of proximate control and also of vicarious social control. Level of aggregation is a crucial consideration in sociological research because it largely determines the feasibility of gathering data through particular procedures. The principal variable in the present control theory is "extent and efficacy of attempted control." The chapter also presents some closing thoughts on the key concepts discussed in the preceding chapters of this book.