_A Father’s Legacy to his Daughter_ was intended only for his own girls, and was not published till after Dr Gregory’s death. During his time in Edinburgh he brought out besides his _Comparative View_, _Lectures on the Duties and Qualifications of a Physician_, which were his introductory lectures, and _Elements of the Practice of Physic_, a first volume of a text-book for his students which he did not live to complete. He thought medicine required a more comprehensive mind than any other profession, and often brought much besides mere technical knowledge into his lectures. As a speaker he was simple, natural and vigorous. He lectured only from notes, ‘in a style happily attempered,’ said one of his contemporaries, ‘between the formality of studied composition, and the ease of conversation.’ On one thing he insisted, that every student should appreciate the limitations of medicine, for only so could they learn to extend its borders.
During these years, too, he carried on a constant correspondence with James Beattie, Professor of Moral Philosophy in Aberdeen, and a poet. Both Beattie and Thomas Reid, who held the corresponding chair in Glasgow, were engaged in combating the teaching of David Hume, which had become very fashionable, and Gregory, though much attached to David Hume as a man, feared him as a teacher, and dreaded the growth of that scepticism which marked the time—a tendency quite as bitterly lamented in England by Samuel Johnson.
‘I am well convinced,’ Gregory wrote to Beattie in a letter dated Edinburgh, 16th June 1767, ‘that the great deference paid to our modern heathens has been productive of the worst effects. Young people are impressed with an idea of their being men of superior abilities, whose genius has raised them above the vulgar prejudices, and who have spirit enough to avow openly their contempt of them. Atheism and Materialism are the present fashion. If one speak with warmth of an infinitely wise and good Being, who sustains and directs the frame of nature, or expresses his steady belief of a future state of existence, he gets hints of his having either a very weak understanding, or of his being a very great hypocrite.... You are the best man I know to chastise these people as they deserve, you have more Philosophy and more wit than will be necessary for the purpose, though you can never employ any of them in so good a cause.’