Boran Berčić, in the second volume of his recent book "Filozofija" , offers two responses to David Chalmers’s conceivability or modal argument against physicalism. This latter argument aims at showing that zombies, our physical duplicates who lack consciousness, are metaphysically possible, given that they are conceivable. Berčić’s first response is based on the principle of the uniformity of nature that states that causes of a certain type will always cause effects of the same type. His second response is based on (...) the assumption that the basic statements of physicalism in philosophy of mind are or should be contingently true. I argue that if Berčić’s first defence is aimed at the conceivability of zombies, it is unsatisfactory. Moreover, I argue that a quite similar argument, offered by John Perry in his book "Knowledge, Possibility and Consciousness" , is afflicted by a similar problem. Nevertheless, under a more plausible interpretation, Berčić’s argument might be taken to attack the metaphysical possibility of zombies. This version of the argument might be effective and has the merit to point out a so far overlooked link between the discussion of the Chalmers’s conceivability arguments against physicalism and the modal strength of causal links and natural laws. Then, I argue that Berčić’s second defence of physicalism, which cannot be combined consistently with his first one, in any case, should not be formulated in the terms of contingent physicalism. (shrink)