We review the bourgeoning literature on ethno-racial diversity and its alleged effects on public trust and cohesion in the context of the evolution of the concept of social capital and earlier claims about itsmanifold positive effects. We present evidence that questions such claims and points to the roots of civicness and trust in deep historical processes associated with race and immigration.We examine the claims that immigration reduces social cohesion by drawing on the sociological classics to show the forms of cohesion that actually keep modern societies together. This leads to a typology that shows ``communitarianism” to be just one such form and one not required, and not necessarily ideal, for the smooth operation of complex organizations and institutions. Implications of our conclusions for future research and immigration policy are discussed.