But even this solitude is not the last issue of Reid’s bête noire. The system in which I have been educated, he said, not only leaves me absolutely alone; it extinguishes me, along with the external universe of things and persons; it is at last literally suicidal. It transforms persistent personal existence into a mere succession of unconnected sensations and ideas. If the magic circle of sensations and ideas, within a self that persists amidst perpetual changes, cannot be broken through, then even this supposed ‘self’ must be an illusion, and the word self must be meaningless. The personal pronoun ‘I,’ as well as the personal pronoun ‘you,’ are both alike unmeaning. The universe resolves at last, not merely into sensations that are all referable to myself, but into sensations without any self—into isolated sensations—which seem indeed to follow one another in an orderly way, but without any guarantee that the seeming order is more than transitory, or that the illusory cosmos may not at any moment become chaos.
Is there nothing within the resources of reason to arrest this intellectual suicide? Has reason got anything to show in justification of this preliminary sacrifice of a conviction on which men have to act, whatever their theories may be? Must I surrender the conviction, that when I am seeing or touching I am actually having revealed to me something that is extended and solid, and that, as such, must be more and other than the private sensations and ideas of the person that is seeing and touching? Must this conviction, and others like it, on which human experience practically depends, be all sacrificed on the altar of authority and conjecture?
This had been the question around which Reid’s thoughts were revolving in the twenty years preceding the publication of his book. ‘For my own satisfaction,’ he tells us, ‘I entered into a serious examination of the principles upon which this sceptical system is built; and was not a little surprised to find that it leans with its whole weight upon a hypothesis which is ancient indeed, and hath been very generally received by philosophers, but of which I could find no solid proof. The hypothesis I mean is—that we do not really perceive things that are external, but only certain images and pictures of them imprinted upon the mind, which are called “impressions” and “ideas.” I thought it unreasonable, upon the authority of philosophers, to admit an hypothesis which, in my opinion, overturns all philosophy; all religion and virtue, and all common sense; and I resolved to inquire into this subject anew, without regard to any hypothesis.’
To accept as a spiritual fact the judgment of human nature, which assures me that when I am seeing or touching I am ‘face to face’ with a reality that exists independently of my changing sensations or ideas, instead of trying in vain by reasoning to prove the existence of this reality by means of intervening sensations and ideas,—this was the alternative he adopted. I dismiss the unwarranted supposition that only my own mind and its invisible contents can be immediately manifested to me; and I fall back on the perception I have of something solid and extended, and therefore more and other than a mere sensation or idea, as what is present to me when I see and touch. Recognition of the fact that our five senses somehow bring us into a consciousness of what is neither a transitory sensation nor an idea of a sensation, but something independent of me, and that would continue to exist after I individually had ceased to exist—this recognition of external realities is Reid’s key to sound philosophy. It is a displacement of the so-called ‘ideas’ of the philosophers, and of fallacious inferences founded upon them, and a substitution of the common reasonable sense, or common judgment of reason, which neither requires nor admits of logical proof. Reid might say that what is most worth proving cannot be logically proved. We all have a direct perception of external reality which cannot be eradicated by reasoning. Abolition of the prejudice which interposed reasonings founded on unreal ideas between our perception and the solid and extended reality, seemed to Reid, in virtue of its far-reaching consequences, to be the chief good he had as a philosopher secured to mankind. In his old age he writes thus to Dr. Gregory:—
‘The merit of what you are pleased to call my philosophy lies, I think, chiefly in having called in question the common theory of ideas, or images of things in the mind, being the only objects of thought—a theory founded on natural prejudices, and so universally received as to be interwoven with the structure of language. Yet, were I to give you a detail of what led me to call in question this theory, after I had long held it as self-evident and unquestionable, you would think, as I do, that there was much of chance in the matter. The discovery was the birth of time, not of genius; and Berkeley and Hume did more to bring it to light than the man that hit upon it. I think there is hardly anything that can be called mine in the philosophy of mind which does not follow with ease from the detection of this prejudice.’
Yet Reid’s Inquiry has been condemned as an unphilosophical appeal from the thoughtful to vulgar intelligence, making the unreflecting many supreme judges in questions intelligible only to the reflecting few. His employment of ‘common sense’ to express the regulative principle of his philosophy would put his book outside philosophical literature, if this term were taken as a synonym for unreasoned opinion—the average judgments of the man in the street. Reid’s own account of what he means by common sense, not to speak of Hume’s recognition of the ‘deeply philosophical’ character of the argument in the Inquiry, should protect him against this imputation. He describes the common sense to which he constantly appeals as ‘the first degree of reason,’ and as having for its office ‘to judge of things self-evident.’ As such, he contrasts it with reasoning, or ‘the second degree of reason, which draws conclusions that are not self-evident from the self-evident judgments of the common sense.’ This distinction between the common rational sense, on which a knowledge of the universe, like the human, which falls short of omniscience, must ultimately turn, and those judgments that are reached by logical reasoning, corresponds to what the Greeks distinguished as noetic and dianoetic power of reason in man. Reid’s genuine judgments of the common sense may be regarded as the divinely inspired response to questions which can be determined for man only by this ideal man latent in us all—judgments verified by the insanity that is implied in resisting them in our actions.
As obtrusive examples of judgments of the common sense, Reid takes the logically undemonstrable convictions (1) of the existence of things external to and independent of me and my perceptions; (2) of my individual personal existence, and continuous personal identity; and (3) of the uniformity, and therefore interpretability, of nature, implying that I may form conclusions about what I have not experienced by what I have experienced. I cannot demonstrate the truth of these judgments: I can only justify them in reason by showing that human nature responds to them, and forbids me to reject them in my actions, on pain of being judged a lunatic, whatever I may say in my speculative theories. ‘Such original and natural judgments,’ he says, ‘are part of the furniture which nature hath given to the human understanding. They are the inspiration of the Almighty. They serve to direct us in the common affairs of life, when our reasoning faculty would leave us in the dark; they are part of our constitution; all the discoveries of our reason are grounded upon them; they make up what is called the common sense of mankind. A remarkable deviation from them, arising from a disorder in the constitution, is what we call lunacy, as when a man believes that he is made of glass. When a man suffers himself to be reasoned out of the principles of common sense by metaphysical arguments, we call it metaphysical lunacy, which differs from the other species of the distemper in this, that it is not continued, but intermittent; it is apt to seize the patient in solitary and speculative moments; but when he enters into sanity, Common Sense recovers her authority.’
It is the first of these three examples of the common sense that is the subject of the Inquiry—intended as preliminary to others which may follow. ‘A clear enumeration and explication of the principles of common sense’ was henceforward Reid’s ultimate aim; but thus far he took those involved in our experience when we are tasting, or smelling, or hearing, or touching, or seeing. As axioms and definitions are the preliminaries of abstract mathematical reasonings, so our sensuous perceptions through the five senses are the preliminaries to reasonings about concrete realities in the world of change. The leading principle of the Inquiry is, that something extended, solid, and movable is directly manifested in our sensuous experiences, equally with the direct manifestations of our own sensations and other feelings when we are conscious of them; and also that we are obliged by common sense to regard extended, solid, and movable things as other than mere transitory sensation or idea. Extended things, large or small, refuse to be melted down into sensations or states of one’s private consciousness. Take this specimen of philosophical argument for accepting perceptions which cannot be logically demonstrated, but which the common sense of human nature refuses to reject:—