In this paper we aim to offer a balanced argument to motivate (re)thinking about the mental illness clause within the insanity defence. This is the clause that states that mental illness should have a relevant causal or explanatory role for the presence of the incapacities or limited capacities that are covered by this defence. We offer three main considerations showing the important legal and epistemological roles that the mental illness clause plays in the evaluation of legal responsibility. Although we acknowledge that these advantages could be preserved without having this clause explicitly stated in the law, we resist proposals that deny the importance of mental illness in exculpation. We argue, thus, that any attempt at removing the mental illness clause from legal formulations of the insanity defence should offer alternative ways of keeping in place these advantages.