Intellectual historians have tended to focus either on shifts in sensibility or, more analytically, on the substance and structure of thought. They might usefully, however, examine both, as well as the reciprocal action of the one upon the other. This applies equally to political and religious ideas. In early twentieth-century Ireland, it was the relationship between religion and politics that stirred controversy. How would the institutions of church and state function, respectively, under Home Rule and the Union. Opposing camps advanced competing prognostications. This contest forces us to rethink the claim that revolutionary insurgency in Ireland was a species of ‘political religion’. The evidence points to a more complex picture while at the same time highlighting the persistence of sectarian attitudes in the historiography of the period.