That mind in the form of will is the only known active power is another prominent lesson in Turnbull’s teaching. ‘It is will alone that manifests power or productive energy. To speak of any other active power in the universe is to speak without meaning; because experience, the source of all the materials of our knowledge, does not lead us to any other conception of power.’ Turnbull’s conception of the material world is very like Berkeley’s. Matter is the established or natural order in which sense ideas present themselves. ‘Properly speaking, what we call matter and space are only sensible ideas, produced in us, according to an established or natural order, by some external cause; for when we speak of material things, we can only mean certain sensible perceptions that arise in our minds, according to a fixed order, but which are experienced to be absolutely inert or passive, having in themselves no productive force.’ It was in this philosophy that Turnbull’s most famous pupil was educated at Marischal College. Turnbull’s official connection with the College lasted only six years. After inaugurating moral philosophy in the modern spirit in Scotland, he resigned in the spring of 1727, and, after some residence abroad, lived in London, producing books in excess of the demand for them. He ended by taking orders in the Irish branch of the Anglican Church, finding the communion of Jeremy Taylor and Berkeley more suited to his temper than the fervid Presbyterianism to which he was accustomed in his youth. In search of health, he died at the Hague in 1749. I have enlarged on Turnbull, because by him Reid was first attracted to the study of the human mind. But Blackwell, the Professor of Greek, must not be forgotten. Blackwell, as well as Turnbull, was connected with Berkeley. It was when Reid was at Marischal College that Berkeley was engaged in the most romantic missionary enterprise of that age, for spreading Christian civilisation in America by a College in the Bermudas. Curiously, Blackwell was one of those whom he asked to join the little party of missionaries who embarked with him at Gravesend in September 1728, after he had surrendered high preferment in Ireland in order to devote his life to a more cosmopolitan philanthropy. The Aberdeen regent was not prepared for the sacrifice. He refers thus to Berkeley’s adventure:—