Karl Popper lamented the prevalence of dogmatic argument in philosophy and commended the kind of critical argument that is found in the sciences. David Miller criticises the uncritical nature of so-called critical thinking because of its attachment to dogmatic arguments. I expound and clarify Popper’s distinction between critical and dogmatic arguments and the background to it. I criticise some errors in Miller’s discussion. I reaffirm the need for philosophers to eschew dogmatic arguments in favour of critical ones.