Dugald Stewart, when illustrating the changes in human memory that are connected with disease and old age, refers thus to Reid:—‘One old man I have myself had the good fortune to know, who, after a long, an active, and an honourable life, having begun to feel some of the usual effects of advanced years, has been able to find resources in his own sagacity against most of the inconveniences with which they are commonly attended; and who, by watching his gradual decline with the courage of an indifferent observer, and employing his ingenuity to retard its progress, has converted even the infirmities of old age into a source of philosophical amusement.’ For sixteen years Reid had been discharging that part of the duties of a professor which belongs to the class-room: the remaining sixteen years of his life, devoted to original research and authorship, illustrate the words of Stewart. He continued, after the appointment of Arthur, to live as before in the Professors’ Court in old Glasgow College—a placid, methodical life, steadily industrious, a sagacious interpreter of nature and of man, still active in the academic senate—with occasional recreation in visits to the country. The year 1780 was saddened by another of those domestic sorrows which formed the chief interruption to the tranquil happiness of his life; for his eldest son, George, died in Newfoundland in February, at the age of twenty-five. Two years later the only remaining son, David, was taken away; after which his daughter, Mrs. Carmichael, alone survived of the nine sons and daughters. Very soon after he had been released from the public work of the professorship, letters to his cousin, Dr. James Gregory, then an Edinburgh Professor of Medicine, speak of activity in transforming the lectures into the form of philosophical essays for publication. This enterprise was indeed Reid’s principal employment for the next eight years. The _Essays_ appeared in two instalments, in 1785 and 1788. The first instalment was a matter-of-fact inquiry into the intellectual power of man; the second was a matter-of-fact inquiry into man’s moral power: the ‘facts’ inquired about and appealed to were the invisible ones of which men are conscious, not those that can be seen and touched—above all, the final convictions of which the Common Sense consists. Both instalments appeared in the same decade of last century in which Kant’s ‘_Kritiks_’ of Pure and Practical Reason were given to the world.