From this misery he sought refuge in the exercise of his mind. His residence at Aberdeen had brought him into the society of several among his countrymen who were engaged in researches well suited to employ his attention to its utmost stretch. Of these the names of Reid, author of An Inquiry into the Human Mind on the Principles of Common Sense--and Campbell, Principal of Marischal College, author of An Essay on Miracles, are the most distinguished. His own correspondence with his friends about this time evinces deep concern at the progress of the sceptical philosophy, diffused by the writings of Hobbes, Hume, Mandeville, and even, in his opinion, of Locke and Berkeley. Conceiving the study of metaphysics itself to be the origin of this mischief, in order that the evil might be intercepted at its source, he proposed to demonstrate the futility of that science, and to appeal to the common sense and unsophisticated feelings of mankind, as the only infallible criterion on subjects in which it had formerly been made the standard. That his meaning was excellent, no one can doubt; whether he discovered the right remedy for the harm which he was desirous of removing, is much more questionable. To magnify any branch of human knowledge beyond its just importance may, indeed, tend to weaken the force of religious faith; but many acute metaphysicans have been good Christians; and before the question thus agitated can be set at rest, we must suppose a certain proficiency in those inquiries which he would proscribe as dangerous. After all, we can discover no more reason why sciolists in metaphysics should bring that study into discredit, than that religion itself should be disparaged through the extravagance of fanaticism. To have met the subject fully, he ought to have shewn that not only those opinions which he controverts are erroneous, but that all the systems of former metaphysicians were so likewise. The Essay on Truth, in which he endeavoured to establish his own hypothesis, being finished in 1769, he employed Sir William Forbes and Mr. Arbuthnot to negotiate its sale with the booksellers. They, however, refused to purchase it on any terms; and the work would have remained unpublished, if his two friends, making use of a little pious fraud, had not informed him that the manuscript was sold for fifty guineas, a sum which they at the same time remitted him, and that they had stipulated with the booksellers to be partakers in the profits. The book accordingly appeared in the following year; and having gained many admirers, was quickly followed by a second impression, which he revised and corrected with much pains.