Get started

WorkThomas Reid

An Inquiry into the Human Mind on the Principles of Common Sense

Hume's skepticism answered one sense at a time, from smell to sight, by a college teacher in Aberdeen.

by Thomas Reid358 passages held

  • English, the original language, and your language
Sign in or subscribe to discuss this work See it in context
First published
(aged 54)
Original language
English

Report a rights issue

Overview

Until David Hume's Treatise of Human Nature appeared in 1739, Reid says in the dedication, he had never thought of doubting what philosophers taught about the human understanding. What they taught, and what this book rejects, was the theory of ideas: the mind perceives not things but images of them, and must reason its way from those images to a world. René Descartes and John Locke built on it, George Berkeley used it to deny that matter exists, and Hume carried it on until even the mind was left as nothing but a sequence of impressions and ideas. Reid's answer is that the starting point was wrong. A sensation is a sign, not a picture: we are so made that the feeling of hardness makes us conceive of a hard body and believe it is there, and beliefs of this kind — the principles of common sense — need no proof and can have none. He argues this one sense at a time, from smell up to sight. In the chapter on seeing he works out a geometry of how things look to the eye, in which the angles of a triangle add up to more than two right angles. In 1972 the philosopher Norman Daniels proposed that this is the first non-Euclidean geometry on record, a claim debated ever since. The chapters began as lectures at King's College, Aberdeen, and as papers read to a philosophical club there. Hugh Blair, the Edinburgh preacher, passed part of the manuscript to Hume, who answered in February 1763 with a courteous letter; Reid replied that he would always count himself Hume's disciple in metaphysics. The book came out in 1764, the year Glasgow elected Reid to the chair Adam Smith had left. It reached a fourth edition by 1785 and was translated into French in 1768 and German in 1782. Joseph Priestley, the chemist and dissenting minister, attacked it at length in 1774, and in 1783 Immanuel Kant put Reid first in his list of Hume's opponents who had missed the point of Hume's problem.

Key concepts

What is the theory of ideas that the Inquiry sets out to overturn?

The view that the mind perceives not things but images of them, called ideas or impressions, and must reason its way from those to a world. Reid finds it in Descartes, Locke, Berkeley and Hume, and argues that, followed honestly, it leads step by step to skepticism: first the secondary qualities go, then matter, then the mind itself, leaving only a train of impressions and ideas.

What is a natural sign in Reid's Inquiry?

A sign whose connection with what it signifies is set up by nature, not by human agreement. Reid distinguishes three classes: those whose connection we discover by experience, as the laws of nature are discovered; those we read without learning, as a face signifies anger; and those that suggest something we had no notion of before, as a sensation of touch suggests hardness and a body that has it.

What separates original from acquired perception?

Original perceptions come from our constitution alone; acquired ones are learned through experience. By sight we originally perceive only colour and visible figure. That an object is far away, or that a sound is a coach passing in the street, is acquired: the mind has learned to read one sign as another, so quickly that the learning is forgotten and the result feels like simply seeing or hearing.

What does the Inquiry mean by the principles of common sense?

Beliefs our constitution leads us to hold that neither need proof nor admit of it: that the things we perceive exist, that the course of nature will continue, that other people speak the truth. Every chain of reasoning, Reid argues, has to start from such principles, so rejecting them in the name of reason leaves reason with nothing to start from. Their authority comes from our being made so.

What is the geometry of visibles?

The geometry of figures as they appear to the eye, before the mind reads them as tangible bodies. Since visible figure depends only on direction from the eye, it behaves like figure drawn on a sphere centred there: straight lines become great circles, and the angles of a triangle add up to more than two right angles. Reid presents it as a geometry with rules of its own.

What are the principles of veracity and credulity?

Two matched parts of our constitution. The principle of veracity inclines people to speak the truth, so that lying takes an effort the truth does not; the principle of credulity inclines us to believe what others tell us, strongest in children and later limited by experience. Without the second, Reid argues, a child would learn almost nothing, since belief in testimony has to come before any means of testing it.

Themes of the book

What this book returns to, gathered into themes and ordered by how much of the text each one occupies.

Sensations as Signs, Not Pictures

What does a feeling of hardness have in common with the hard table it reports? Nothing at all, the book answers, and that is why perception cannot be a matter of copies.

The theory of ideas assumed that a sensation resembles its object, so that knowing the image meant knowing the thing. Reid finds no resemblance anywhere: the smell of a rose is a feeling in the mind, and a feeling can be like nothing but another feeling. Nature has instead made sensations signs, as a word is the sign of its meaning, and by our constitution they suggest a quality and a belief that it is present. He calls this a natural language, and argues that people could never have agreed on an artificial one without first understanding the looks, tones and gestures nobody teaches.

  • perception
  • sensation
  • signs
  • natural signs
  • language
  • secondary qualities
  • mind
  • mind-body problem

Enter a dialogue

Common Sense Against the Skeptic

Must every belief show its credentials to reason before it may be held? The book answers that the beliefs perception forces on us come from the same workshop as reason and deserve the same trust.

Hume had shown, Reid grants, where the theory of ideas leads when it is followed honestly: to no world, no mind, nothing but a train of impressions. Rather than accept the conclusion, Reid turns back on the premise. Belief in an external object, he writes, is none of his manufacture; it came from the mint of nature. A skeptic who trusts reason and doubts the senses has no ground for the preference, since both faculties came from one maker. And nobody lives the doubt: whoever resolves not to believe his senses breaks his nose against a post and ends in a madhouse.

  • skepticism
  • common sense
  • belief
  • external world
  • ideas
  • empiricism
  • reason
  • epistemology

Enter a dialogue

The Geometry of Seeing

What does the eye actually present before habit turns it into distance, size and solid bodies? The longest chapter answers with a geometry of appearances that obeys rules of its own.

Visible figure, Reid argues, is a sign the mind passes over at once to reach the tangible thing it signifies, which is why hardly anyone notices it. Attended to for itself, it has a geometry: projected from the eye, straight lines become arcs of great circles, and the angles of a triangle exceed two right angles. A blind mathematician such as Saunderson could work it out without ever seeing. The same chapter weighs rival accounts of why two eyes see one object single and why squinting can double it, and traces single vision to corresponding points on the two retinas.

  • vision
  • visual perception
  • optics
  • binocular vision
  • retinal correspondence
  • attention

Enter a dialogue

Trusting Nature and Each Other

Why does a child believe what it is told, and expect fire to burn tomorrow as it did today? Neither expectation comes from reasoning, the book argues, and without both nobody would ever learn to reason.

Near its close the Inquiry names two principles that work as a pair. The principle of veracity inclines us to speak the truth, and the principle of credulity to believe what others tell us, long before we could weigh a witness. Beside them the inductive principle leads us to expect that the course of nature will hold. Hume traced such expectations to custom; Reid replies that they appear before custom could have formed them and belong to our constitution. The credulity that experience later corrects is what made experience possible in the first place.

  • induction
  • laws of nature
  • habit
  • causation
  • analogy
  • philosophy of science
  • memory

Enter a dialogue

Within this work

passages held
358
distinct concepts
305
by passages held, corpus-wide
#211

What this book thinks together

The wheel takes this book’s leading concepts and shows how often they come up together. The wider the band between two, the more of its passages speak of both. Among them, most often together: “perception” and “vision”.
Concept co-occurrence, strongest first 8 concepts, joined by 20 pairings. 85 pairings reach beyond these concepts and are not drawn.
ConceptPaired conceptShared passages
perceptionvision45
perceptionsensation29
perceptionvisual perception20
beliefperception15
common senseskepticism13
perceptionskepticism13
perceptionphilosophy of mind10
beliefskepticism9
common senseperception8
beliefcommon sense7
philosophy of mindskepticism6
common sensesensation5
philosophy of mindsensation5
sensationvisual perception5
beliefsensation4
sensationskepticism4
common sensephilosophy of mind2
visionvisual perception2
philosophy of mindvisual perception1
sensationvision1

Works held

The author's work in order, this book marked in place. Your-language title first, the original beneath it where the two differ; side chips show which full texts are held.

  1. 1748 An Essay on Quantity

    A sixteen-page paper, published sixteen years before Reid's first book, the Inquiry into the Human Mind.

     EN
  2. 1764 An Inquiry into the Human Mind on the Principles of Common Sense you are here EN
  3. 1774 A Brief Account of Aristotle's Logic, with Remarks

    A chapter in another man's book rather than a book of its own, and the fullest account of formal logic that Reid published.

     EN
  4. 1785 Essays on the Intellectual Powers of Man

    The book many scholars now rank as Reid's greatest, and the one that sets out his theory of knowledge in full.

     EN
  5. 1788 Essays on the Active Powers of Man

    Companion to the Intellectual Powers, turning from how we know to how we act; the last of Reid's books.

     EN
Sign in or subscribe to discuss this work

— or open another of their works