Jeffrey, from his unsigned review of Sardanapalus, The Two Foscari and Cain, Edinburgh Review
Of Cain, a Mystery we are constrained to say, that, though it abounds in beautiful passages, and shows more power perhaps than any of the author's dramatical compositions, we regret very much that it should ever have been published. It will give great scandal and offence to pious persons in general, and may be the means of suggesting the most painful doubts and distressing perplexities, to hundreds of minds that might never otherwise have been exposed to such dangerous disturbance. Philosophy and Poetry are both very good things in their way; but, in our opinion, they do not go very well together. It is but a poor and pedantic sort of poetry that seeks to embody nothing but metaphysical subtleties and abstract deductions of reason, and a very suspicious philosophy that aims at establishing its doctrines by appeals to the passions and the fancy.