Article ID: JAF4415 | By: Adam C. Pelser

This article first appeared in the Christian Research Journal, volume 41, number 5 (2018). For further information or to subscribe to the Christian Research Journal please click here.

My students sometimes ask me who my favorite philosopher is. I’m never quite sure how to answer that question because it feels a bit like being asked which one of my children is my favorite. But when I’m pressed, I can’t help but mention the Scottish Presbyterian minister-philosopher Thomas Reid (1710–1796). Although he is often given short treatment in discussions of the major figures in the history of modern philosophy, Reid was one of the most important philosophers of the eighteenth century. He was also arguably the most important critic of philosophical skepticism since Augustine and a model Christian philosopher.

Much of Reid’s philosophical writing was focused on critiquing the skepticism of the atheist Scottish philosopher David Hume, but Reid consistently presented his criticisms in winsome ways. Hume even remarked in a letter to their mutual friend, Hugh Blair, that Reid’s work was “written in a lively and entertaining manner & will be able to fix the Attention even of those who are the {least} curious about metaphysical Reasonings.”1 It would be an understatement to say that some great philosophers are not great writers. By contrast, Reid’s philosophical wisdom is equally matched by his literary wit. Contemporary philosopher Nicholas Wolterstorff rightly judges that Reid “was the greatest stylist of all who have written philosophy in the English language. No one can match him for wit, irony, metaphor, humor, and elegance.”2 It is thus a great pleasure for me to introduce others to the philosophy of Thomas Reid.


Reid grew up as the son of a Presbyterian minister in Strachan, a village located in the Grampian Highlands of Scotland, about twenty miles southwest of Aberdeen. Following in his father’s footsteps, Reid entered ministry in the Church of Scotland, which appointed him minister of New Machar in 1737. Having studied philosophy at Marischal College, Aberdeen, Reid continued to read widely in philosophy during his years in ministry, and in 1948 he presented his first published philosophical essay to the Royal Society. Consequently, Reid was selected for the position of regent at King’s College in 1751. He later went on to hold the prestigious Chair of Moral Philosophy at the University of Glasgow where he succeeded another great Scottish philosopher, Adam Smith.

A deeply insightful and faithful minister-philosopher, Reid serves as a wonderful example of how Christian ministry and philosophy can complement one another. There are many Christians today who are inclined to think of academic philosophy and Christian ministry as diametrically opposed vocations, but Reid helps us to see that this has not always been the case. Nor need it be today.

Reid made lasting contributions to many areas of philosophy, but his most important contributions include his “common sense” philosophical methodology and his theory of perception together with its attendant epistemology. We cannot appreciate the significance of Reid’s philosophical views, though, without first understanding a particular philosophical view that he sought to oppose throughout his career.


Much of Reid’s philosophical writing challenged a family of views that he called “the Theory of Ideas” (or “the Way of Ideas”). Essentially, the Theory of Ideas holds that when we perceive material objects through our five senses, we are not directly aware of the objects that we perceive; rather, we are only directly aware of our sensations or ideas of those objects. On this view, it is as though we only ever see the world indirectly through its sidelong reflection on the mirror of our minds.

The problem with this way of thinking about perception, Reid argued, is that it leads to a far-reaching skepticism of the sort defended by David Hume. For, if we are directly aware only of the ideas in our minds, what reason do we have for thinking that they accurately represent the world outside our minds? By way of analogy, if we were stuck in a locked room for our entire lives and only shown pictures of the world outside the room, what reason would we have for believing that the pictures are accurate representations of the world? Moreover, what reason would we have for believing there is any world outside the room at all? Perhaps the mirror of our minds inaccurately reflects the world like a distorted fun-house mirror. Or perhaps it isn’t a mirror at all, but an elaborate hologram machine that makes us believe physical objects such as trees and birds exist even though they really do not. The slope from the Theory of Ideas to radical skepticism is slippery indeed.

The problem is further complicated, according to Reid, by the fact that the sensations we experience in perception in no way resemble the objects as we perceive and believe them to be. For example, the feeling we experience when we press our hands against a hard table does not at all resemble the property of hardness that we naturally believe the table to possess once we’ve touched it. Therefore, our sensations do not show us what the world is like through any kind of resemblance.

Reid suggested that many of his philosophical predecessors, including Rene Descartes, John Locke, and George Berkeley, assumed versions of the Theory of Ideas without realizing how it leads to skepticism. He writes, “The theory of ideas, like the Trojan horse, had a specious appearance both of innocence and beauty; but if those philosophers had known that it carried in its belly death and destruction to all science and common sense, they would not have broken down their walls to give it admittance.”3 After seeing in Hume’s A Treatise of Human Nature how the Theory of Ideas culminates in radical skepticism, Reid set out to demonstrate its falsehood and defend an alternative theory of perception.


Reid argued that there are certain basic facts that all humans rationally believe even though we are unable to give arguments for them. Reid called such basic facts “first principles of common sense.” As a point of philosophical methodology, Reid maintained that all good philosophy must begin with the first principles of common sense. Any philosophical theory that would force us to give up first principles must be rejected as not only false but also absurd. He explains, “It is a bold philosophy that rejects, without ceremony, principles which irresistibly govern the belief and the conduct of all mankind in the common concerns of life, and to which the philosopher himself must yield, after he imagines he hath confuted them. Such principles are older, and of more authority, than Philosophy: she rests upon them as her basis, not they upon her. If she could overturn them, she must be buried in their ruins.”4

According to Reid, the fact that the external material world exists is a first principle of common sense. We are right, therefore, to reject skepticism about the material world, along with the Theory of Ideas that gives rise to it, even if we cannot refute it with an argument. In fact, Reid contends that no such argument can be found. Since all good reasoning must start with the first principles of common sense, it is impossible to argue for belief in the first principles from some more basic fact. So rather than attempting to prove the existence of the external material world through argument, Reid skillfully employed humorous ridicule and other rhetorical devices to demonstrate the absurdity of skepticism: “I resolve not to believe my senses. I break my nose against a post that comes in my way; I step into a dirty kennel; and, after twenty such wise and rational actions, I am taken up and clapt into a mad-house. Now, I confess I would rather make one of the credulous fools whom Nature imposes upon, than of those wise and rational philosophers who resolve to with-hold assent at all this expence.”5

Through his poignant insistence that philosophical theories must bow to the first principles of common sense, Reid fathered the Common Sense school of Scottish Philosophy.


But if the Theory of Ideas has it wrong, how should we think about the nature of perception? Reid suggests that the sensations we experience in perception function as “natural signs” that point to the reality of the objects and properties that they signify. So, when we experience the sensation of touching a hard table, the sensation or feeling that we experience naturally and immediately causes us to think of the table as hard and to believe that the hard table exists — not because our sensation resembles the hard table but simply because God created us to form such a belief when we experience the corresponding sensation.

Reid argued that since we simply find ourselves directly perceiving and believing in the external material world by way of natural signs, we are right to trust those perceptions, despite the skeptic’s arguments for doubting them. “Reason, says the skeptic, is the only judge of truth, and you ought to throw off every opinion and every belief that is not grounded on reason. Why, Sir, should I believe the faculty of reason more than that of perception; they came both out of the same shop, and were made by the same artist; and if he puts one piece of false ware in my hands, what should hinder him from putting another?”6

In his later work, Reid extended his focus beyond sense perception to argue on similar grounds that we are right to trust other common sources of belief including the testimony of others, our innate moral sense, and even our aesthetic taste through which we perceive beauty.


Contemporary Christian philosophers and apologists have made extensive use of Reid’s epistemological insights. In particular, the approach to religious knowledge known as “reformed epistemology” is Reidian through and through. Alvin Plantinga and Nicholas Wolterstorff, the two primary champions of reformed epistemology, have argued extensively that belief in God can be rational and warranted even in the absence of arguments proving the existence of God. According to Plantinga, Christian belief typically is not based on arguments but is rather “properly basic” and functions epistemically very much like one of Reid’s first principles of common sense.7

C. Stephen Evans’s book Natural Signs and Knowledge of God (Oxford University Press, 2010) is another important application of Reid’s philosophy to religious epistemology. In this insightful book, Evans argues that some of the traditional arguments for God’s existence — and other evidence besides — function like Reidian natural signs that point us to the existence and character of God. Ryan West and I have built on Evans’s argument by showing how it is possible to perceive God through perceptions of natural beauty.8 For, as Reid himself observed, “Other minds we perceive only through the medium of material objects, on which their signatures are impressed.…The invisible Creator, the Fountain of all perfection, hath stamped upon all his works signatures of his divine wisdom, power, and benignity, which are visible to all men.”9 In these ways and others, Reid is responsible for inspiring and informing much contemporary thinking about the epistemological warrant for Christian belief.

Reid also can serve as an exemplar of charitable discourse for today’s Christian philosophers and apologists. Despite their deep disagreements, in a letter to Hume dated 1763, Reid wrote, “A little Philosophical Society here [Aberdeen]…is much indebted to you for its entertainment. Your company would, although we are all good Christians, be more acceptable than that of St. Athanasius; and since we cannot have you upon the bench, you are brought up oftener than any other man to the bar, accused and defended with great zeal, but without bitterness. If you write no more in morals, politics, or metaphysics, I am afraid we shall be at a loss for subjects. I am respectfully Sir, Your most obliged humble Servant, Tho. Reid.”10 Sadly, some aspiring Christian apologists today do not even treat fellow Christians with such respect and fair-mindedness. Whatever we think about his common-sense approach to philosophy, we would all do well to follow Reid’s commitment to charitable disagreement and dialogue.11

Adam Pelser is associate professor of philosophy at the U.S. Air Force Academy. He teaches and writes on ethics and philosophical theology and he is currently writing a book on emotions in the Christian life.


  1. “The Hume–Reid Exchange,” in Thomas Reid, An Inquiry into the Human Mind on the Principles of Common Sense, ed. Derek R. Brookes (University Park, PA: Pennsylvania State University Press, 1997), 256. Hereafter, I will refer to this work simply as Reid’s Inquiry.
  2. Nicholas Wolterstorff, Thomas Reid and the Story of Epistemology (Cambridge: Cambridge University Press, 2001), 1.
  3. Inquiry, 75–76.
  4. Inquiry, 21.
  5. Inquiry, 170. For a defense of Reid’s rhetorical use of ridicule, see Daniel M. Johnson and Adam C. Pelser, “Foundational Beliefs and Persuading with Humor: Reflections Inspired by Reid and Kierkegaard,” Faith and Philosophy 31, 3 (2014): 267–85.
  6. Inquiry, 169.
  7. Alvin Plantinga, Knowledge and Christian Belief (Grand Rapids, MI: Eerdmans, 2015) 64–65.
  8. Ryan West and Adam C. Pelser, “Perceiving God through Natural Beauty,” Faith and Philosophy 32, 3 (2015): 293–312.
  9. Thomas Reid, Essays on the Intellectual Powers of Man, ed. Derek R. Brookes (Edinburgh: Edinburgh University Press, 2002) VIII iv, 602–3.
  10. “The Hume–Reid Exchange,” Inquiry, 264–65. Spelling and capitalization modernized for clarity.
  11. The views expressed in this article are those of the author and do not necessarily reflect the official policy or position of the United States Air Force, the United States Department of Defense, or the United States government.