https://doi.org/10.36253/ds-15898
Scottish Common Sense Philosophy: Twelve Theses
Trent University, Canada
Abstract. What was Scottish common sense philosophy? Understood in purely historical terms, this question is easily answered: it was a school of thought which came into being during the middle third of the 18th century, and which formed a vital part of that many-sided whole now known as the Scottish Enlightenment. But what was its philosophical content? Answering this question is the raison d’être of the present essay. In what follows, I shall identify twelve theses which are central to the distinctive brand of common-sensism articulated by Reid and Stewart. My modus operandi is simple: after stating each thesis, I shall summarize the principal arguments for it and explain its philosophical significance.
Keywords: Scottish Enlightenment, common sense, scepticism, Thomas Reid, Dugald Stewart.
Contents
Thesis 1: Philosophy is first and foremost an inquiry into the nature of the human mind
Thesis 6: The domains of mind and matter are known immediately, but in fundamentally different ways
Thesis 8: Pace Hume, our basic concepts are not derived directly from experience
Thesis 10: Lockean representative realism cannot be correct
What was Scottish common sense philosophy? Understood in purely historical terms, this question is easily answered: it was a school of thought which came into being during the middle third of the 18th century, and which formed a vital part of that many-sided whole now known as the Scottish Enlightenment. To be more precise, this philosophical movement or school originated in Aberdeen, where members of the so-called “Wise Club” – the Aberdeen Philosophical Society, established in 1758 – met periodically to read their work to each other, to drink decent wine in moderation, and to discuss the ingenious sceptical arguments of David Hume (1711-1776)1. The Wise Club’s most notable member was Thomas Reid (1710-1796), whose first book – An Inquiry into the Human Mind on the Principles of Common Sense (1764) – earned him the Chair of Moral Philosophy at Glasgow, which Adam Smith (1723-1790) had recently vacated. After Reid gave up teaching in 1780, he published two substantial volumes based on his lecture notes: Essays on The Intellectual Powers of Man (1785) and Essays on the Active Powers of Man (1788). Reid’s first set of Essays addressed central questions in the theory of knowledge, metaphysics, and the philosophy of mind. The second set dealt with the foundations of morality, moral psychology, and the philosophy of action.
Although Reid was by far the ablest philosopher to emerge from the womb of the Wise Club, three of the Society’s other members merit a mention: the Presbyterian divine George Campbell (1719-1796), author of Dissertation on Miracles (1762) and The Philosophy of Rhetoric (1776); Alexander Gerard (1728-1795), another Presbyterian divine, whose An Essay on Taste (1759) and An Essay on Genius (1774) did much to promote the study of aesthetics; and James Beattie (1753-1803), the poet and intemperate polemicist whose best-selling An Essay on The Nature and Immutability of Truth In Opposition to Sophistry and Scepticism (1770) attacked Hume’s irreligious scepticism – and modern philosophy in general – with considerable vehemence. Like Reid, all these thinkers taught in Aberdeen, either at King’s College (founded in 1495) or Marischal College (founded in 1593).
After Reid’s death in 1796, the leading exponent of the so-called “Scottish philosophy” was his friend and erstwhile pupil Dugald Stewart (1753-1828), who held the Chair of Moral Philosophy at the University of Edinburgh. Although he lacked Reid’s originality, Stewart’s range as a philosopher was much broader, partly because he had a feeling for the history of ideas which Reid lacked, and partly because of his abiding interest in social, political, and economic questions. No doubt the breadth of Stewart’s outlook owed a good deal to the influence of his teacher Adam Ferguson (1723-1816), author of An Essay on the History of Civil Society (1767), Institutes of Moral Philosophy (1769), and Principles of Moral and Political Science (1792).
In addition to being a superb lecturer, Stewart was a prolific writer, and his elegantly written books were favourably received outside of the British Isles. His major works were the following: Elements of the Philosophy of the Human Mind in three volumes (1792, 1814, 1827), Outlines of Moral Philosophy (1793), Philosophical Essays (1810), Philosophy of the Active and Moral Powers, and three volumes of Dissertations (1815, 1821, 1854). In these and other writings, Stewart presents Reid’s common sensism as the culmination of modern thought, and not (as in Beattie) a moralistic repudiation of it.
So much for the early history of Scottish common-sensism2. But what was its philosophical content? Answering this question is the raison d’être of the present essay. In what follows, I shall identify twelve theses which are central to the distinctive brand of common-sensism articulated by Reid and Stewart. My modus operandi is simple: after stating each thesis, I shall summarize the principal arguments for it and explain its philosophical significance3.
Thesis 1: Philosophy is first and foremost an inquiry into the nature of the human mind
a. Philosophy and the Human Mind: Philosophy has understood itself in many ways: as knowledge of the One beyond the mutable Many; as the study of Being qua Being; as an inquiry into the fundamental causes or reasons of things; as the search for an ideal reality behind beguiling appearances; as the attempt to view the world under the aspect of eternity; as a chapter in the Zeitgeist’s Bildungsroman (to name only a few). According to Thomas Reid and Dugald Stewart, philosophy is primarily the study of the human mind and its powers. Now, why did they think this?
b. Two Kingdoms: Scientific inquiry has its origin in our natural desire to account for known phenomena. As Reid and Stewart point out, however, the known universe consists of two domains: a material world outside us and an intellectual world within. Therefore, the domain of Mind is no less worthy of study than the domain of Matter.
c. The Cartesian Cogito: If you can doubt the testimony of your senses, you can doubt the existence of a material world. Yet it is impossible for you to doubt your own existence as a doubter, because you cannot doubt or think anything unless you are something. Reid and Stewart are thus convinced that Descartes was right: no knowledge is more certain than the knowledge you have of your own mind, which is known to you in a way you know nothing else.
d. The Proper Study of Mankind: Socrates forsook the study of Nature for the study of Man. However, philosophers cannot shed much light on the human condition unless they examine our distinctively human capacities: the intellectual powers by which we acquire knowledge of various kinds, and the active powers which make the practice of virtue possible. Consequently, philosophers cannot afford to neglect the study of these powers.
e. The Foundations of Education: Education aims at the harmonious cultivation or perfection of our intellectual faculties. But we cannot cultivate a thing if we are ignorant of its nature, and we cannot perfect a thing whose proper function is wholly unknown to us. Nor can we harmonize powers or faculties unless we understand how they are supposed to fit together. Therefore, education cannot hope to attain its aim unless it is preceded by a systematic examination of our faculties.
f. The Pursuit of Happiness: Happiness, the highest good for human beings, comes from the development of what is highest and best in our nature – namely, our intellectual and active powers. Since we cannot develop these powers unless we understand them, the pursuit of happiness ought to be grounded in knowledge of their nature. Progress in moral philosophy consequently depends on a detailed and comprehensive anatomy of the human mind.
g. Leibniz or Locke? Once philosophers realize that they cannot know truths about a world inaccessible to non-philosophers (as in Plato and Leibniz), they must work within our shared conceptual scheme (as in Aristotle and Locke). In that case, the aim of philosophy is not to justify our core beliefs, but to understand what the human mind must be like in order to produce them. Simply put, Reid and Stewart think philosophy must be more descriptive than prescriptive.
h. Naturalized Epistemology: According to Reid and Stewart, philosophers cannot say how human beings ought to form beliefs unless they understand how beliefs are actually formed. However, the laws or principles which govern the processes of belief-formation are not knowable a priori. Therefore, philosophers cannot identify the normative criteria for knowledge or rational belief without the help of a descriptive science of mind.
i. The Vast Ocean of Being: Since humans are insatiably inquisitive, we need to know whether there are fixed limits to what our minds can know; otherwise, time and energy will be wasted, and inquirers will eventually succumb to epistemic despair. Consequently, we ought to inquire into the limitations of our faculties before we inquire into anything more recondite or recherché. Locke was the first to say this clearly, and Reid and Stewart are convinced he was right.
j. Image of God: Since our knowledge of God must be derived from our knowledge of what He has created, and since everything created by God is fundamentally good, all His works are worthy of study. But Reid regards the human mind as the noblest work in Nature; and the nobler the creature, the more clearly it reveals the perfections of its Creator. Therefore, Mind is more worthy of study than Matter.
Thesis 2: The human mind contains certain original principles of belief or innate belief-forming dispositions
a. A Science of Mind: How are we to study the human mind? According to Reid and Stewart, we must employ the method which has worked so splendidly in physics, astronomy, and optics: that of inductive reasoning founded firmly on fact. In other words, knowledge of mind (like knowledge of matter) must be based on patient and scrupulous observation, not on a priori speculations or fanciful hypotheses.
b. Belief and Judgment: If Reid and Stewart are correct, we should bracket metaphysical questions about what the mind is, attending instead to what the mind does. That is to say, we begin by distinguishing a wide variety of mental operations, referring each type of operation to a faculty or power (intellectual or active) exerted by the human mind. To see how this is supposed to work, consider the phenomenon of judgment or belief. For the purposes of illustration, here are a few of the things that I believe: that I am seated by the fire with a piece of paper in my hand; that I am thinking about a park in Taormina; that I had pancakes for breakfast yesterday; that the Young Pretender died in exile; that Palestrina was a better composer than Geminiani; that the sun will rise tomorrow; that it was wicked of Cain to slay Abel; and that 7 + 5 = 12. Why do I believe these things? Simple, reply Reid and Stewart: because I have evidence for them. But what exactly is the nature of that evidence? Before we unpack their answer to this question, let us consider three dialogues between a common-sense believer, A, and a sceptical philosopher, B.
c. Beliefs About the Present: A: I am seated by the fire. B: And why do you believe that? A: Because I perceive it by means of my senses: I see the fire, feel its warmth, smell the smoke, and hear the crackle of the shifting logs. There is no doubt in my mind. B: But why do you believe what you call your senses? Why suppose their testimony is evidence for anything? A: I cannot help taking this for granted; ‘the constitution of my nature’ (to use a favourite phrase of Reid’s) will not allow me to doubt it.
d. Beliefs About the Past: A: Yesterday I made pancakes for breakfast. B: And why do you believe that? A: Because I distinctly remember reading over the recipe, setting out the ingredients, and preparing the dish in my kitchen. Again, there is no doubt in my mind about any of this. B: But why do you believe what you call your memory? Why suppose its testimony is ever evidence for anything? A: Once again, this is something I cannot help taking for granted; the constitution of my nature will not allow me to doubt it.
e. Beliefs About the Future: A: The sun will rise tomorrow. B: And why do you believe that? A: Because the sun has always risen in the past. B: But why do you believe that Nature is uniform? Why suppose that the fact that things have always happened a certain way in the past is evidence that things will continue to happen that way? A: Yet again, this is something I cannot help taking for granted; the constitution of my nature will not allow me to doubt it.
f. Fundamental Principles: These dialogues reveal two things which Reid and Stewart regard as vitally important. The first is that belief-formation ultimately depends on a set of fundamental assumptions about what constitutes evidence. These assumptions have been called by various names: laws of human belief, first principles, principles of common sense, primary truths, and canons of evidence (among others). Whatever one chooses to call them, they include the following: that I exist; that I am the same person I was yesterday; that my faculties of knowledge – consciousness, perception, memory, reason, and conscience – are fundamentally trustworthy; that there is a material world existing independently of perception; that there are minds other than my own; that the future will resemble the past; that every event must have a cause; that there is a real distinction between right and wrong; and that I am morally responsible for some of my actions.
g. Innate Principles: The second thing is that these fundamental assumptions seem to be innate or instinctive, not learned or acquired. Why? Reid and Stewart rest their case on the following observations. (1) Far from being peculiar to the present age, these things have been taken for granted by human beings in all times and places of which we have knowledge. (2) These assumptions are not the effects of education or experience, because we accept them long before we are taught anything. Indeed, it seems we cannot learn anything unless we accept them. (3) Although we may question these assumptions in theory, we must take them for granted in practice. Philosophers are free to doubt, but agents are obliged to believe. (4) These assumptions are not opinions or theories which we happen to hold; they are unshakeable dogmas imposed upon our minds by Nature. (5) Denying these assumptions strikes us as ridiculous or absurd – the sort of thing no-one in his right mind would say and mean. (6) These assumptions are so fundamental that we do not even think of them as assumptions until the philosophical sceptic makes us aware of them. (7) We cannot give any reasoned defence of these assumptions, but we do not think they need any, because it seems to us that argument could add nothing to their authority.
h. Summary: According to Reid and Stewart, we cannot explain the phenomenon of belief-formation unless we assume the human mind comes into the world with certain fixed dispositions. The beliefs directly produced by these instinctive dispositions are what we may call natural convictions or common sense commitments. Note that this part of the Reid-Stewart account is purely descriptive: it does not tell us whether our natural convictions are rational, or whether our innate dispositions can be trusted.
Thesis 3: The reliability of our innate belief-forming dispositions cannot be established by reasoning or argument
a. The Impossibility of Proof: How can I be sure that my innate belief-forming dispositions are not wildly unreliable? Reid freely concedes that sceptics are indisputably right about this much: we can never prove that our faculties are trustworthy, or that our natural convictions are true. Think of it this way: in order to prove a proposition, you must reason from premises which are more evident to you than the thing you intend to prove, and nothing is more evident to us than the truth of our natural convictions. Therefore, the truth of our common sense picture of the world cannot be established by argument.
b. Proof and Circularity: If I think a class of natural convictions stands in need of justification, I must think the reliability of the original principle which generates them cannot be taken for granted. But I cannot know or believe anything at all, Reid observes, unless I take the reliability of some natural belief-forming principle for granted. Unfortunately for me, the reliability of this second principle is no more evident than that of the first. Consequently, attempts to justify common sense commitments are always question-begging.
c. Proof and Prejudice: Anyone seeking to justify a proposition with an argument must assume our faculty of reason can be trusted. But reason is one of our belief-forming dispositions. Therefore, a philosopher who tries to prove that our innate belief-forming dispositions can be trusted has assumed something which is no more evident than the thing he seeks to prove. Our philosopher, Reid concludes, has thus shed all prejudices save one: her arbitrary partiality for reason.
d. An Illustration: Consider a concrete example: How can I know whether Nature is uniform, so that the future will resemble the past? As this question concerns a contingent matter of fact, it cannot be settled by a priori argument. Yet no argument from experience can settle it, because the authority of experience is the very point at issue. In the end, Reid agrees with Hume: our belief in the uniformity of Nature has no foundation in reasoning.
Thesis 4: Philosophy is impossible unless there are first principles: intrinsically credible premises which need no proof
a. Evidence ≠ Argument: Here is another thing Reid thinks sceptics are right about: we should not be unduly credulous, or allow ourselves to believe things for which we lack sufficient evidence. However, he agrees with Adam Ferguson that it is one thing to say that nothing is to be believed without evidence, but quite another to say that nothing is to be believed without argument. Since a failure to insist on this distinction has wrought havoc in philosophy, several things need to be made insultingly clear.
b. A Regress of Reasons: In the first place, the view that justification is always a matter of supporting one belief with another generates a regress of reason-giving. That is, A would derive its justification from its relation to B, B would derive its justification from its relation to C, C would derive its justification from its relation to D, and so on ad infinitum. Reid reaches the same conclusion as Aristotle: no proposition can be justified by argument unless some propositions can be believed without argument.
c. Foundationalism or Absolute Scepticism: If no body of knowledge or science can dispense with first principles, either none of our judgments can be justified (absolute scepticism) or there must be some intrinsically credible judgments for which no argument is needed (foundationalism). But the view that none of our judgments can be justified cannot itself be justified. To put it another way, absolute scepticism is indefensible: anyone who argues for it has ipso facto assumed it is false, and no-one who accepts it can possibly think its acceptance is reasonable.
d. Absolute Scepticism and Philosophy: According to Reid, philosophers cannot accept absolute scepticism. Is this because absolute scepticism is counterintuitive, or sure to be met with incredulous stares? No; it is because philosophers who endorse absolute scepticism have voluntarily exiled themselves from what Wilfrid Sellars (1912-1989) christened “the space of reasons” – a discursive framework which makes argument and justification possible. But philosophy cannot live outside the space where justification takes place. Absolute scepticism is thus a rejection of philosophy, not a position within it.
e. Philosophy and Foundationalism: To sum up Reid’s reasoning: since philosophy is a form of inquiry, and inquiry aims at knowledge, philosophy must accept some form of foundationalism. “Very well,” one might say, “but why must this foundation be made with the mud and straw of common sense?”
Thesis 5: Philosophy is impossible unless our natural convictions or common sense commitments are first principles
a. Exculpation: Even Hume, the prince of sceptics, admits that Nature will not permit us to doubt certain things. But if there are things Nature will not let us doubt, Reid observes, we can hardly be blamed for believing them. Does this mean these beliefs must be true? No; but if they are false, the fault is not ours, and there is nothing we can do about it. So what is the point of saying that no one should believe the things which everyone must believe?
b. Theory and Practice: Reid frequently reminds us that sceptics always accept natural convictions in practice; they only claim to doubt such things in the rarified sphere of theory. But is a purely theoretical doubt – one without any conceivable practical consequences – really a doubt at all? To defend an affirmative answer to this question, it seems, we would have to commit ourselves to propositions whose truth is much less evident to us than the truth of our natural convictions.
c. Practical Postulates: What are common sense commitments, really? According to Reid, they are practical postulates – the things which everyone must assume in order to engage with the world and others. These unavoidable presuppositions of human action thus do not need any theoretical justification or grounding, because the conditions of possible practice determine the limits of theory. Consequently, philosophy must adopt these humble articles of faith as its first principles.
d. Common Sense and the Examined Life: As lovers of wisdom, philosophers are expected – rightly – to wrestle with questions about how we ought to live. However, these fundamental questions about morals and politics are only meaningful for people who think within the framework of our common sense commitments. Philosophy thus condemns itself to irrelevance, Reid concludes, unless philosophers have faith in our shared ineradicable judgments.
e. Common Sense and Piety: If our most basic and entrenched beliefs are not self-evident, our cognitive faculties cannot be trusted. In that case, three possibilities present themselves: (1) there is no God; (2) God is incompetent (assuming our Maker did His best); or (3) God is deceitful (assuming He could have done better). Unbelief in philosophy and in religion thus go hand in hand – a point repeatedly made by James Beattie in his crusade against Hume.
f. Either-Or: Unless our common sense picture of the world is true, we do not have the faintest idea of what truth is. According to Reid, we must draw one of two conclusions: either common sense judgments are first principles which need no justification, or there are no first principles. But the latter view is equivalent to absolute scepticism – a doctrine no-one can accept in theory or in practice. Philosophy thus must rest on common sense, not common sense on philosophy.
g. Doubt and Foundations: I cannot doubt any class of natural convictions without calling into question the reliability of the original principle or faculty which produced them. But in order to call that principle into question, Reid points out, I must rely on some other principle which has no more intrinsic authority than the first. Hence it makes perfect sense to doubt the second – assuming it made sense to doubt the first. Doubting common sense beliefs thus requires one to doubt what makes doubt possible.
h. Unreasonable Doubt: In order to doubt a proposition, we need reasons or grounds which are more evident to us than that proposition. But if Reid is right, nothing is more evident to us than the truth of our common sense beliefs. Therefore, any attempt to doubt our ordinary beliefs will depend on things which are no less dubitable than the things to be doubted.
i. Common Sense and Ordinary Language: Since language is made in the image of common sense, the acceptance of our common sense frame of reference is a condition of communication. But then this frame of reference requires no justification, since what we call justification is only possible within it. Since we cannot understand the sceptic if she is sincere, Reid thinks it is pointless to argue with her and attempt to show her the error of her ways.
j. Common Sense and Inquiry: Inquiry aims at the discovery of truth, so inquirers must assume that truth is not wholly unknowable. But they cannot assume truth is not wholly unknowable unless they assume their faculties can be trusted – at least under certain conditions. Therefore, philosophy is impossible unless philosophers assume that ordinary judgments normally need no justification.
Thesis 6: The domains of mind and matter are known immediately, but in fundamentally different ways
a. Two Domains, Two Faculties: How are mind and matter known? Here Reid and Stewart start with a soothing platitude: the faculty through which you know your own thoughts and sensations is not the same as the faculty through which you know trees, rocks, and stars. Far from being the invention of philosophers, this elementary distinction is embedded in ordinary language: a person ‘perceives’ trees and rocks, we say, whereas she is ‘conscious’ of her thoughts or sensations. The inner world of mind is thus known by the faculty of consciousness; the outer world of matter, by the faculty of perception.
b. Consciousness and Perception: Yet there is much less to this dictum than meets the philosophic eye, Reid and Stewart tell us, because ‘perception’ here means no more than ‘that faculty or intellectual power (whatever it is) by which we observe things in the external world,’ and ‘consciousness’ means no more than ‘that faculty or intellectual power (whatever it is) by which we observe the contents of our minds.’ So the claim that bodies are known by perception and minds by consciousness is not an ‘explanation’ of anything.
c. Implications: However, that platitude was never intended to explain anything; it was meant to remind us of a familiar fact whose implications are easily overlooked. (1) Since Mind and Matter are known in fundamentally different ways, they constitute what Stewart calls “distinct objects of study.” (2) Since the domains of perception and consciousness do not overlap, neither faculty can give us a reason to doubt the other. (3) Since there is no proof that either is trustworthy, it would be inconsistent to trust one of these faculties but not the other. (4) It follows that only two positions are internally consistent: either mind and matter can both be known immediately, or neither can be known at all.
Thesis 7: We only perceive sensible qualities, and we are only conscious of thoughts and sensations. Nevertheless, we naturally or spontaneously believe in the existence of both matter and mind
a. Perception and Belief: Strictly speaking, Reid and Stewart tell us, we do not perceive bodies; we only perceive sensible qualities – extension, colour, figure, and the like. Thanks to a law of our constitution, however, our perception of these qualities immediately and irresistibly leads us to believe in two things: the present existence of the qualities we perceive, and the present existence of something else – an object or unthinking substance – to which the qualities in question belong.
b. Matter and Qualities: To put it another way, I cannot perceive qualities as such without thinking of them as qualities of something. This means I cannot perceive qualities without positing something which is not a quality – namely, a material object or unthinking being. However, sensible qualities are the sole objects of perception. Therefore, I cannot believe in the existence of what I perceive unless I believe in something which no-one can perceive: an invisible substratum called body or matter.
c. Consciousness and Belief: Similarly, Reid and Stewart claim that you are not conscious of your mind per se; you are only conscious of its contents – thoughts, sensations, desires, volitions, and so on. Thanks to a law of our constitution, however, your consciousness of these thoughts and sensations immediately and irresistibly leads you to believe in two things: the present existence of your thoughts and sensations, and the present existence of something else – a subject or thinking substance – to whom these thoughts and sensations belong.
d. Mind and Thoughts: To put it another way, I cannot be conscious of thoughts as such without regarding them as mine. This means I cannot be conscious of thoughts without positing something which is not a thought – namely, a mind or self-conscious being. However, thoughts and their ilk are the sole objects of consciousness. Therefore, I cannot believe in the existence of what I am conscious of at this moment unless I believe in something which no-one can ever be conscious of: an active, thinking principle called mind, soul, self, ego, or I.
e. The Relativity of Human Knowledge: So far, Reid and Stewart have advanced two weighty claims. (1) We cannot doubt that matter and mind exist, because an unshakeable and non-inferential belief in each is a spontaneous effect of our constitution. (2) We cannot know what mind and matter are in themselves, or apart from their relation to phenomena with which we are directly acquainted (sensible qualities in the case of matter, thoughts and the like in the case of mind). The moral – stressed more by Stewart than by Reid – is that our conceptions of mind and matter are inescapably relative and limited. But if nothing can be known or thought about the inner nature of either, materialists are dogmatists sans le savoir; for they gleefully boast of knowing things which exceed all human capacity.
f. The Scottish Synthesis: If the Reid-Stewart view is correct, the seemingly irreconcilable insights of their predecessors can be synthesized. (1) Berkeley was right to deny that we perceive anything except qualities, just as Hume was right to deny that we are conscious of anything other than perceptions. (2) Descartes and Locke were right to affirm the reality of material substance, because we cannot help believing that trees and rocks are more than bundles of sensible qualities. (3) Similarly, Descartes and Berkeley were right to affirm the reality of a substantial self, because we naturally believe there is more to our ‘I’ than a series of ephemeral perceptions. (4) Descartes and Berkeley were also right to point out that knowledge of one’s own existence does not depend on knowledge of anything material or mind-independent. (5) Although Descartes and Locke were right to credit us with knowledge of material objects, Berkeley and Hume were right to deny that such knowledge can ever be derived or inferred from the contents of one’s own mind.
Thesis 8: Pace Hume, our basic concepts are not derived directly from experience
a. Beyond Empiricism: Reid and Stewart call our attention to three facts. (1) We must believe in the existence of mind and matter. (2) We cannot believe in things of which we can form no conception. (3) Your mind is never an object of consciousness, and matter is never an object of perception. What does all this mean? According to Reid and Stewart, it means that the human constitution is such that we can and must form conceptions of things which are not objects of possible experience. The broader moral is clear: since the hypothesis that the mind is a tabula rasa cannot account for the facts, we must reject the empiricist theory of concept-formation endorsed by Locke, Berkeley, and Hume.
b. The Priority of Fact over Theory: This way of arguing reveals a major methodological difference between Hume and Reid. Time and time again, Hume argues as follows: “All our ideas are copies of impressions; but we have no impression of X; therefore, we have no idea of X.” No matter what X stands for (mind, matter, or causation), Reid’s riposte is the same: “True, we have no impression of X; but we do have an idea of X; therefore, not all our ideas are copies of impressions.” Reid thus takes his stand on the flatlands of fact, whereas Hume looks down on the data from the dizzying heights of theory.
c. Morality and Mind: As Francis Hutcheson (1694-1746) and Richard Price (1723-1791) pointed out, our basic moral concepts – duty and obligation, right and wrong, good and evil – are neither ideas of sensation (perception) nor ideas of reflection (consciousness). Therefore, one of two things must be true: either Locke’s theory of the mind and its powers is incomplete, or our moral judgments are not what we think they are. Reid backs the first option; Hume, the second. Once again, the underlying issue is a meta-philosophical one: What should be given more weight – a seductively simple hypothesis favoured by philosophers, or the fixed and unyielding convictions of the vulgar?
Thesis 9: There is no defensible alternative to metaphysical realism, which has the status of a first principle
a. Metaphysical Realism: Metaphysical realism is the thesis that ordinary physical objects – trees and rocks – exist independently of perception and knowledge. To put it another way, the metaphysical realist denies that objects in the spatiotemporal world are reducible to coherent sets of appearances, representations, or mere bundles of ideas. Realism is this sense is thus plainly incompatible with Berkeleyan idealism, phenomenalism, or solipsism.
b. Realism and Natural Convictions: As far as Reid is concerned, metaphysical realism is not a daring theory championed by the few; it is a way of thinking which no-one can avoid. To be more precise, Reid thinks that (1) we cannot help believing in the existence of trees and rocks because we cannot help believing that we perceive them, and (2) we cannot help believing that what we perceive exists independently of perception. Assuming both propositions state facts, metaphysical realism is a first principle. Accordingly, no proof of realism’s truth is possible or necessary.
c. Realism or Absolute Scepticism: Our knowledge of mind-independent things should not be questioned, Reid thinks, because we cannot doubt that the testimony of perception is fundamentally trustworthy. At this point, the sceptic is sure to protest: “But surely we need to prove that perception is trustworthy before we can claim to have knowledge of the external world.” Reid’s rejoinder is simple but powerful: if we needed to know that a faculty was reliable in order to know truths through it, nothing could ever be known in any domain. Consequently, we have a choice: accept absolute scepticism and forswear philosophy for good, or admit the reliability of our faculties qualifies as a first principle.
d. The Fallibility of Perception: Undeterred, the intrepid sceptic may advance another objection: “But it makes sense to question the reliability of perception, because we know for a fact that our senses have deceived us.” This time, Reid has a two-pronged reply at the ready. (1) The principle which underpins this objection leads straight to absolute scepticism. After all, if it were necessary to prove the reliability of any faculty known to be fallible, ‘who should ’scape whipping’? Reason is known to be fallible; yet the sceptic does not demand a proof of its reliability – and quite rightly. If anyone should demand such a proof, it would be impossible to satisfy them, since reasoning could never convince them of anything. Moreover, we cannot reason or make inferences without relying on the evidence of memory; yet memory, like perception and reason, is known to be fallible. (2) Recall that consciousness is to the inner world of mind what perception is to the external world of matter. Since the domains of perception and consciousness do not overlap, perception alone can give us a reason to doubt perception. In other words, it seems you can never have any positive reason to distrust the testimony of your senses unless you trust their testimony most of the time. But if your claim to know that your senses are fallible must depend on knowledge acquired through your senses, the argument from perceptual fallibility to perceptual scepticism is incoherent.
e. Knowledge of Fallibility: The following imaginary dialogue clarifies Reid’s position. Reid: I grant that our senses are fallible. But how do you know that your senses have ever deceived you? Sceptic: I discover that they have deceived me when I compare my perceptions of the same object under different conditions. For example, the tower of the castle looks round from far away; when I get closer to it, I can see the tower is really square. Reid: So your belief that your senses initially deceived you in this case depends on the evidence of your senses? Sceptic: Correct. Reid: You see, you do trust perception after all; otherwise, you would have no grounds for doubting it. To put it another way, you cannot know that the premise of your argument (‘My senses have deceived me’) is true unless you assume that your argument’s conclusion (‘Sense-perception is untrustworthy’) is false. Consequently, you are not entitled to conclude that perception is untrustworthy tout court; you can only conclude that it is untrustworthy under certain conditions – as when things are seen from far away, from an unfavourable vantage-point, or through a medium, or in poor light.
f. All or Nothing: According to Reid and Stewart, only two epistemological stances are internally consistent: either mind and matter can both be known immediately, or neither can be known at all. But if knowledge of matter is as epistemically immediate as knowledge of mind, the sceptic’s question – “How can we know mind-independent things, such as trees and rocks, when we are directly acquainted with nothing but our perceptions?” – depends on a patently indefensible assumption. There is thus no need to excogitate specious ‘proofs’ of an external world, or to look for a privileged class of perceptions whose correspondence to reality is guaranteed, or to wrangle interminably with idealists, phenomenalists, or solipsists. To put it another way, philosophers who doubt the existence of material objects have no right to believe in the existence of their minds.
Thesis 10: Lockean representative realism cannot be correct
a. Representationalism: Most early modern philosophers seem to have agreed that nothing is ever before the mind in any of its multifarious operations except ideas or impressions: fleeting states or representations which have no existence apart from our awareness of them. Assuming this way of thinking about the mind and its contents is correct, the immediate object of sense-perception must always be an appearance or an image, never a material or mind-independent thing.
b. Representationalism and Realism: What happens when philosophers conjoin the theory of ideas with metaphysical realism (as Locke seems to have done)? In the first place, they must deny that mind-independent things or their qualities can ever be perceived immediately. But if we never perceive material objects immediately, Berkeley and Hume argued, we can never know anything about them. Reid finds himself in complete agreement with Berkeley and Hume. Why?
c. Berkeley and Hume: Four arguments put forward by Berkeley and Hume seem to have struck Reid as especially persuasive. (1) If the contents of my mind alone are self-evident to me, I can never know whether any of my perceptions accurately represent the external world. Indeed, I cannot even know that there is such a world, for its existence is no more than a bare possibility. (2) If ideas resemble nothing but other ideas, they cannot represent a mind-independent world (assuming there is such a thing). But the material world cannot be known through ideas if our ideas are not representations. (3) If I am only aware of ideas, I cannot conceive of anything that does not resemble them (assuming, again, that ideas can only resemble other ideas). Therefore, I cannot even think of a mind-independent reality. (4) According to Locke, the difference between primary qualities and secondary qualities can be captured by saying that only our ideas of the former actually resemble anything in the body. But if our ideas of primary qualities resemble primary qualities, primary qualities must themselves be ideas. The distinction between primary and secondary qualities thus collapses if the theory of ideas is true.
d. Anti-Representationalism: Philosophers who accept the theory of ideas, Reid concludes, must accept one of two views in the end: external world scepticism (Hume) or subjective idealism (Berkeley). Since both views contradict our first principles, and since whatever contradicts first principles is untenable, the theory of ideas must be rejected.
Thesis 11: Representationalism is false. That is, ideas and impressions are not the immediate objects of perception
a. The Status of Ideas: Reid has much more to say about the weaknesses of representationalism. To begin with, ideas are not data; they are posits or theoretical entities which are supposed to explain how our minds work. But knowledge of the human mind must be based on fact and observation, not on hypothesis and conjecture. Moreover, the theory’s defenders model their understanding of mind on their understanding of matter. But if mind and matter are distinct objects of study, we have no right to assume that their operations are analogous.
b. The Nature of Ideas: Since ideas are supposed to be mind-dependent items with which we are directly acquainted, it seems there cannot be more or less to them than meets the inner eye of consciousness. As Reid sees it, this means the truth about our ideas should be manifest, not hidden. Why, then, is there so much disagreement about their nature among philosophers? Unless ideas are fictions invented by philosophers with fertile imaginations, this persistent lack of consensus is hard to explain.
c. The Emperor’s New Clothes: Since the theory of ideas is not self-evident, we should not accept it unless it can be made evident by reasoning. According to Reid, however, the theory’s truth is usually assumed by its adherents; and the handful of arguments that have been offered for it are hardly persuasive or unproblematic. So why is this theory held as a dogma by philosophers who lecture us on the duty of proportioning one’s beliefs to the evidence? Even first-rate minds, Reid suggests, have their prejudices.
d. The Illusion of Explanation: The theory of ideas was supposed to account for certain facts about the human mind and its operations – perception, memory, consciousness, conception, and so on. As far as Reid is concerned, it explains none of these things. Since we do not understand how the mind perceives ideas any better than we understand how the mind perceives external things, one mystery has been surreptitiously and shamelessly substituted for another. It would be more honest for philosophers to acknowledge that we do indeed perceive a mind-independent world, while admitting they are unable to explain how this happens.
e. Common Sense Contradicted: Not only does the theory fail to explain the phenomena; it is actually incompatible with them. That is to say, the theory of ideas denies that what we took to be facts about the mind and its powers (e.g. - that we can think about an extra-mental world, or that we perceive and know material objects) are facts at all. But Reid insists that theory ought to be answerable to fact, not fact to theory - especially when the facts in question are ones our constitution compels us to recognize as facts. In a word, the fact that we cannot explain a phenomenon is no reason to explain it away.
f. Perception and Ordinary Language: In ordinary language, the word ‘perception’ is only applied literally to one’s awareness or experience of external things – tables and chairs, apples and pears. Reid concludes that philosophers who claim we ‘perceive’ ideas are either talking nonsense (in which case they should be corrected and soundly admonished) or they are using the word figuratively or metaphorically (in which case they should be prepared to tell us plainly what they mean by it).
g. A Confusion of Faculties: Although Reid grants that there is a sense in which we are aware of ‘ideas’ (pains, sensations, thoughts), he denies that we either perceive them or fail to perceive them. Since these items are objects of consciousness, not objects of perception, the defenders of ideas can be accused of conflating faculties or reducing perception to consciousness without any justification. To put it another way, talk of ideas seems to confuse two mental acts or operations: perception (in which the object – a tree, say – exists independently of the act by which it is apprehended) and sensation (in which the object – a pain, for instance – is not independent of the act by which it is apprehended).
Thesis 12: Philosophical doubts about the foundations of science, morality, and religion lead to absolute scepticism, and thus to the abolition of philosophy itself
a. The Rationality of Science: According to Reid, there is no proof that the future will resemble the past, or that there is an external world, or that events always have causes, or that our faculties of reason and sense-perception are reliable. But these are not eccentric commitments or opinions; they are the unsought axioms by which everyone lives. Therefore, the fact that we cannot prove them is no reason to cast aspersions on the rationality of scientific inquiry.
b. The Foundations of Morality: Reid agrees with Hume that ought-statements cannot be derived from is-statements. However, moral scepticism can be deduced from this premise only if no moral judgments are self-evident. But conscience (or whatever one calls the faculty which generates moral judgments) is an original principle of our constitution, just like perception, consciousness, and memory. Since the authority of original principles is underived, there are only two possibilities: either some moral judgments are self-evident, or nothing is.
c. Moral Liberty and Responsibility: Although metaphysicians cannot demonstrate the reality of free will, we are unable to doubt that people are morally responsible for some of their actions. But you cannot be responsible for an action, Reid thinks, unless you could have done otherwise; and you could not have done otherwise unless you have some degree of power over the determinations of your will. Moral liberty thus must be treated as a first principle, because belief in contra-causal or libertarian freedom is built into our attitude towards ourselves and others.
d. Natural Theology: According to Reid and Stewart, there is no proof that ‘whatever begins to exist must have a cause’ (the major premise of one version of the cosmological argument for theism) or that ‘certain things are signs or evidence of design’ (the major premise of one version of the teleological argument). But neither premise needs any justification, they tell us, because both propositions are metaphysical first principles: ultimate presuppositions which do not derive their justification from anything outside themselves.
e. Miracles and Revelation: Hume’s argument against believing in miracles (and, by extension, revealed religion) assumes that experience is the sole foundation of our faith in testimony. But Hume’s sweeping assertion is not the fruit of patient observation. According to Reid and George Campbell, the facts tell a very different story – namely, that human beings come into the world disposed to believe what we are told by others (the principle of credulity), just as we come into the world inclined to tell others the truth (the principle of veracity). Hence Hume’s attack on miracles is vitiated by its reliance on a false assumption.
f. Body and Soul: Each of us stubbornly believes in the existence of a self which is more than a Humean bundle of perceptions. Therefore, the reality of this substantial self or mind cannot be doubted. But can this mind or soul exist independently of one’s body? This possibility cannot be ruled out on a priori grounds, Stewart argues, because the inner natures of mind and matter are wholly unknown to us. By the same token, no rationalist metaphysician can ever demonstrate that this possibility is more than a possibility.
g. Immortality and A Future State: According to Stewart, belief in immortality can be justified by moral and analogical arguments, not by metaphysical ones. Eschewing demonstrations, Stewart attempts to show that the hypothesis of a future state makes the most sense of various facts about the human constitution: our natural desire for immortality, our endless aspirations towards progress and perfection, the intimations of conscience, and much else besides. So Scottish common sensism is not only a philosophy of natural faith; it is also a philosophy of supernatural hope.
1 Because of space limitations, I pass over the contributions made by Henry Home, Lord Kames (1696-1782), George Turnbull (1698-1748), Francis Hutcheson (1694-46), and James Oswald (1703-1793).
2 Stewart’s de facto successor at Edinburgh was Sir William Hamilton (1788-1856), a charismatic polymath who attempted to wed Reid’s common sense philosophy with the critical philosophy of Kant. As Hamilton belongs to the 19th century, I shall say nothing more about him.
3 This essay builds on the interpretation of Scottish common sense philosophy presented in The Rise and Fall of Scottish Common Sense Realism, Oxford University Press, Oxford 2018. Chapters 1, 3, and 4 of that book provide detailed textual support for the main interpretive claims I make here.