Karl Popper champions an open society in which all institutions, principles and values are open to criticism. Anthony O’Hear contends that Popper’s vision is utopian because an open society can survive only if some non-liberal values are assumed, including the prohibition of criticism of fundamental liberal principles and values. I correct O’Hear’s interpretation of Popper and I rebut most of his criticisms, arguing that an open society is stronger if it permits criticism of all views. However, I accept and strengthen (...) O’Hear’s rejection of Popper’s assimilation of an open society to a scientific community. I also suggest that the survival of open societies may require limits on immigration from societies permeated by Islamic fundamentalism or similar ideologies. (shrink)