Mrs Cockburn here adopted Dr Clarke's theory of the foundations of morality, namely, that the distinctions between virtue and vice are not created by the declarations or even by the will of the Deity, but arise out of eternal and immutable relations and essential differences of things. Not long after, her strength was much worn down by frequent attacks of asthma, to which she had been subject for many years. "I have," she says, "very little prospect of tolerable health for any continuance. My cough returned at the beginning of September, and held me about two months, but is now succeeded by such a difficulty of breathing that I do not know which is most grievous; but between them I am reduced to great weakness." Yet she was at this time engaged upon a new metaphysical work, which proved to be the most elaborate and able of all her literary performances, her "Remarks upon the Principles and Reasonings of Dr Rutherford's Essay on the Nature and Obligations of Virtue, in Vindication of the Contrary Principles and Reasonings Enforced in the Writings of Dr Samuel Clarke." The Rev. Dr Thomas Rutherford, whose essay appeared in 1744, had therein maintained the doctrine that the test and essence of virtue was its tendency to promote the good properly understood, whether of the agent or others; in other words, was utility in the largest sense. When her tract was finished, Mrs Cockburn sent it to Warburton, whose theory on the subject of it was different both from Rutherford's and her own, and against whose views one of her previous works, as we have seen, had been in part directed. Warburton held that the distinction between virtue and vice was constituted by the arbitrary will of the Deity. Notwithstanding this difference of opinion, however, he not only admitted the merit of the present work in the frankest and most cordial terms, styling it, in a letter to the authoress, _the strongest and clearest piece of metaphysics that ever was written_, but took upon himself the charge of finding a publisher for it; and when it appeared in 1747, it was introduced by a preface from the pen of Warburton, in which he almost reiterated those strong expressions, declaring it to contain "all the clearness of expression, the strength of reason, the precision of logic and attachment to truth which makes books of this nature really useful to the common cause of virtue and religion." This work appears to have attracted much more notice than anything that Mrs Cockburn had previously done. She was subsequently induced by the advice of her friends to set about the preparation of a complete collection of her writings, with the view of publishing it by subscription. But this task she did not live to see accomplished. At last, in January 1749, she lost her husband, who appears to have been about a year older than herself; and this stroke probably shortened her own existence, which terminated on the 11th of May of the same year. ELIZABETH BERKELEIGH.