Abstract: This chapter examines judicial activism in the US Supreme Court. For discussions of judicial activism to be analytically illuminating, a reasonably uncontroversial baseline is needed against which activism can be measured. Two candidates for the baseline are considered, each of which holds out some promise of producing some analytic purchase. The avoidance canon measures activism with reference to substantive constitutional law whatever it happens to be; and community expectations measures it with reference to those expectations, again whatever they might be. It is argued that the use of constitutional interpretation as the baseline is more promising than the use of community expectations, but neither is entirely satisfactory.