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.
Reid’s Essays form, as it were, the inner court of the temple of which the Aberdonian Inquiry is the vestibule. But the vestibule is a more finished work of constructive skill than the inner court, for the aged architect appears at last as if embarrassed by accumulated material. The Essays, greater in bulk, perhaps less deserve a place among modern philosophical classics than the Inquiry, notwithstanding its narrower scope, confined as it is to man’s perception of the extended world, as an object-lesson in the method of appeal to the common sense. In the Essays an advance is made towards a finally ethical interpretation of man and the universe.
We have no longer the light of letters to Lord Kames in this closing stage of Reid’s life; for Kames died in 1782. Reid’s retiring modesty deprived him of that large literary intercourse to which his philosophical position might otherwise have led. His correspondence with men eminent in letters or philosophy seems almost confined to Kames, the Gregories, Dugald Stewart, and Dr. Price. I find no trace of correspondence with his Aberdeen friends Campbell and Beattie, whose pursuits had so much in common with his own. But letters to Dr. James Gregory take the place in the ‘eighties’ which those to Lord Kames took in the ‘seventies’; they reveal an old age given to proof-sheets, scientific experiments, and benignant interest in social progress. One dated ‘Glasgow College, April 7, 1783,’ tells of the Essays on the Intellectual Powers in the press:—‘I shall be much obliged if you will continue to favour me with your observations; therefore I have put off examining those you have sent until the manuscripts be returned, which I expect about the end of this month, along with Dugald Stewart’s observations.’ Again he writes in June:—‘I cannot get more copied of my papers till next winter, and indeed have not much more ready. This parcel goes to page 658. I believe what you have got before may be one-half of all I intend. The materials of what is not yet ready for the copier are partly discourses read in our Literary Society, partly notes of my lectures. Your judgment of what you have seen flatters me very much, and adds greatly to my own opinion of it; though authors seldom are deficient in a good opinion of their works. I am at a loss to express my obligations to you for the pains you have taken.’ He refers in another letter to what he regards as the source of the fashionable agnosticism against which his life was a continued philosophical protest:—‘I have often thought of what you propose—to give a History of the Ideal System and what I have to say against it, by itself; and I am far from being satisfied that it stands in the most proper place [in the Essays]. I have endeavoured to put it in separate chapters [e.g. Essay ii. ch. 7-15], whose titles may direct those who have no taste for it to pass over them. I observe that Bayle and others, who at the reformation of Natural Philosophy gave new light, found it necessary to contrast their own discoveries with the Aristotelian notions which then prevailed. We may now wish their works purged of this controversial part; but perhaps it was necessary at the time they wrote, when men’s minds were full of the old system, and prepossessed in its favour. What I take to be the genuine Philosophy of the Human Mind is in so low a state, and has so many enemies, that I apprehend those who would make any improvement in it must, for some time at least, build with one hand, and hold a weapon with the other.’ So Reid claimed the office of modern reformer of the philosophy of human mind, as Bacon and others had been the reformers of the sciences which interpret external nature.
On ‘March 14, 1784,’ he mentions the progress of the book:—‘I send you now the remainder of what I propose to print with respect to the Intellectual Powers of the Mind. It may perhaps be a year before what relates to the Active Powers be ready; and therefore I think the former might be published by itself, as it is very uncertain whether I shall live to publish the latter. I think the title may be Essays on the Intellectual Powers of the Human Mind. It will easily divide into eight Essays; but with regard to this, as well as whether the two parts may be published separately, I wish to have your advice and Mr. Stewart’s. I apprehend that the Second Part—I mean what relates to the Active Powers—will not be near so large as the First.’ On ‘2nd May 1785’ he announces that the Essays on the Intellectual Powers are ready for publication, dedicated to Dr. Gregory and to Dugald Stewart:—‘I send you enclosed what I propose as the title of my Essays, with an Epistle which I hope you and Mr. Stewart will allow me to prefix to them. Whether your name should go first, on account of your doctor’s degree, or Mr. Stewart’s, I leave you to adjust between yourselves. I know not how to express my obligations to you both, for the aid you have given me.’
The book thus ushered into the world in 1785 treats of those constituents of the common sense that are implied, not only in perception of things through the five senses and memory, but also in imagination and in the experimental sciences that deal with the past, the distant, and the future. One of them contains the rudiments of a criticism of the common sense principles that finally regulate all abstract reasonings, and above all, those that determine our judgments of truths contingent upon Will—human and divine; in all of which what philosophers called ‘ideas’ seemed to him to spoil the genuine common sense and its inspirations. The fifth Essay deals with the office and relations of our abstract conceptions. Of this Essay Schopenhauer remarks that ‘the best and most intelligent exposition of the nature and essence of conceptions which I have been able anywhere to find is in Thomas Reid’s Essays on the Powers of the Human Mind. This was afterwards condemned by Dugald Stewart in his Philosophy of the Human Mind. Not to waste paper, I will briefly remark with regard to Stewart, that he belongs to that large class who have obtained an undeserved reputation through favour and friends, and therefore I can only advise that not an hour should be wasted over the scribbling of this shallow writer.’[23] This unworthy criticism of Stewart is far removed from the calm judgment of Reid.
That our perceptions are not related to their objects as effects are related to their causes, is insisted on in the Essays, in opposition to Priestley, who treats cognitive acts as the issue of power which belongs to matter. ‘Men,’ Reid says, ‘have been prone to imagine that, as bodies are put in motion by some impulse or impression made upon them by contiguous bodies, so the mind is made to think and perceive by some impression made upon it by contiguous objects. But to say that an object which I see with perfect indifference makes an impression upon my mind is not good English. It is evident from the manner in which this phrase is used by modern philosophers that they mean, not barely to express by it my perceiving an object, but to explain the manner of perception. They think that the object perceived acts upon the mind in some way similar to that in which one body acts upon another. The impression upon the mind is conceived to be something wherein the mind is altogether passive. But this is a hypothesis which contradicts the common sense of mankind. When I look upon the wall of my room, the wall does not act at all, nor is capable of acting: the perceiving it is an act or operation in me.’ In short, the relation between perceptions and their objects is a unique relation, not to be confounded with the causal, the only causality involved being the percipient power that is in me.
Those Essays of Reid which treat of the constituents of the common sense that are implied in the Intellect power of man, appeared in the early summer of 1785. In September he informed Dr. Gregory of the opinion of Dr. Price, the most eminent contemporary English metaphysician:—‘I had a letter from Dr. Price lately, thanking me for a copy of the Essays I ordered to be presented to him; which he has read, and calls a work of the first value; commends me particularly for treating Dr. Priestley so gently, who, he says, had been unhappily led to use me ill.’ He then refers to his own health, which seems to have suffered from the mental strain, now relieved by the issue of his book:—‘As you are so kind as to ask me about my distemper, I think it is almost quite gone, so as to give me no uneasiness. I abstain from fruit and malt liquor, and take a little port wine, mostly noon and night, not above two bottles a week when alone. The more I walk or ride, or even talk or read audibly, I am the better.’
Dr. Beattie writes thus to the Bishop of Chester in October:—
‘Has your lordship read Dr. Reid’s Essays on the Intellectual Powers of Man? Those readers who have been conversant in the modern philosophy of mind, as it appears in the writings of Descartes, Malebranche, Locke, Berkeley, and Hume, will be much entertained with this work, which does great honour to the sagacity and patience of the author. It contains the principles of his Inquiry, laid down on a larger scale, and applied to a greater variety of subjects. Dr. Reid treats his opponents and their tenets with a respect and a solemnity that sometimes tempt me to smile. His style is clear and simple; and his aversion to the word idea is so great, that I think he never once uses it in delivering his own opinions. It was not without reason that Stillingfleet took the alarm at Mr. Locke’s indiscreet use of that word. It was indeed an ignis fatuus that decoyed him in spite of his excellent understanding into a thousand pits and quagmires. Berkeley it bewildered still more. And it reduced David Hume to the condition of a certain old gentleman of whom we read, that—
Fluttering his pinions vain,