He begins to see that power must be referred to mind or spirit alone, and that matter is powerless. 'Efficient causes are not within the sphere of natural philosophy, which is concerned only with the laws or methods according to which Power operates. It exhibits the grand machine of the material world, analysed, as it were, and taken to pieces. It belongs to metaphysics and natural theology to show the Power that continues and gives motion to the whole; according to laws which the naturalist discovers, and perhaps according to laws still more general.'
It was thus that Reid’s uneventful life of thought—deep, steady, unobtrusive—was sustained for sixteen years, when he was educating the rising generation in the old class-room at the College; unfolding philosophy in correspondence with a sympathetic friend; contributing essays to the Literary Society which met monthly at the College; and preparing his 'Brief Account' of Aristotle—all until he had reached his seventieth year. On the 19th of May 1780 he wrote to Lord Kames of a change that had occurred the day before:—
'I find myself growing old; and I have no right to plead exemption from the infirmities of that stage of life. For that reason I have made choice of an Assistant in my office. Yesterday the College at my desire made choice of Mr. Archibald Arthur, preacher, to be my assistant and successor. I think I have done good service to the College by this, and procured some leisure to myself, though with reduction of my finances.'
It was Reid's desire, while his faculties were yet vigorous, to devote his strength to further philosophical authorship. During the remaining sixteen years of his life his lectures
