What have great philosophers such as Bertrand Russell, George Berkeley, Lewis Carroll, and Charlie Chan said about logic, fallacies, and the importance of logical thinking in life? The quotations below are arranged in alphabetical order by author, from top to bottom. Click on the author's name in the Index just beneath to go directly to that author's quote. If you know of a good quote that should be here, please send it to The Fallacy Files.

Bentham, Jeremy Berkeley, George Carroll, Lewis Chan, Charlie
De Morgan, Augustus Epictetus Fischer, David Hackett Geach, Peter
Hillis, Burton Hitchens, Christopher Huxley, Thomas Henry Jefferson, Thomas
Joubert, Joseph Laplace, Marquis de Mill, John Stuart Nickell, Joe
Peirce, Charles Sanders Russell, Bertrand Truzzi, Marcello Wieseltier, Leon
Wolff, Christian

Jeremy Bentham

Without a popular assembly taking an effective part in the government and publishing its debates, and without free discussion through the medium of the press, there is no demand for fallacies. Fallacy is fraud; and fraud is useless when everything is done by force.1

George Berkeley

Surely it wouldn’t be such a deplorable loss of time if a young gentleman [or young lady] spent a few months [or a few years] on the much despised and decried art of Logic―a surplus of logic is by no means the prevailing nuisance of this age!2

Lewis Carroll

Once master the machinery of Symbolic Logic, and you have a mental occupation always at hand, of absorbing interest, and one that will be of real use to you in any subject you may take up. It will give you clearness of thought—the ability to see your way through a puzzle—the habit of arranging your ideas in an orderly and get-at-able form—and, more valuable than all, the power to detect fallacies, and to tear to pieces the flimsy illogical arguments, which you will so continually encounter in books, in newspapers, in speeches, and even in sermons, and which so easily delude those who have never taken the trouble to master this fascinating Art.3

Charlie Chan

Hasty conclusion like toy balloon: easy blow up, easy pop.4

Augustus De Morgan

It is very commonly said that studies which exercise the thinking faculty, and especially mathematics, are means of cultivating logic, and may stand in place of systematic study of that science. This is true so far, that every discipline strengthens the logical power: that is to say, strengthens most of what it finds, be the same good or bad. It is further true that every discipline corrects some bad habits: but it is equally true that every discipline tends to confirm some bad habits. Accordingly, though every exercise of mind does much more good than harm, yet no person can be sure of avoiding the harm and retaining only the good, except by that careful examination of his own mental habits which most often takes place in a proper study of logic, and is seldom made without it.5


When one of the company said to him [Epictetus], "Convince me that logic is necessary."―Would you have me, he said, demonstrate it to you? "Yes." Then I must use a demonstrative form of argument. "Granted." And how will you know, then, whether I argue sophistically? On this, the man being silent, You see, says he, that, even by your own confession, logic is necessary; since without it, you cannot even learn whether it be necessary or not.6

David Hackett Fischer

Logic is not everything. But it is something—something which can be taught, something which can be learned, something which can help us in some degree to think more sensibly about the dangerous world in which we live.7

Peter Geach

I have been in love with logic ever since my father started me on logic in my teens. Logic of itself cannot give anyone the answer to any questions of substance; but without logic we often do not know the import of what we know and often fall into fallacy and inconsistency.8

Burton Hillis

There's a mighty big difference between good, sound reasons and reasons that sound good.9

Christopher Hitchens

What can be asserted without evidence can also be dismissed without evidence.10

Thomas Henry Huxley

[S]cience is simply common sense at its best; that is, rigidly accurate in observation, and merciless to fallacy in logic.11

Thomas Jefferson

…[I]n a republican nation whose citizens are to be led by reason and persuasion and not by force, the art of reasoning becomes of first importance.12

Joseph Joubert

It is better to debate a question without settling it, than to settle it without debate.13

Pierre Simon, Marquis de Laplace

L'esprit a ses illusions, comme le sens de la vue; et de même que le toucher corrige celles-ci, la réflexion et le calcul corrigent les premières.14

John Stuart Mill

In attempting to establish certain general distinctions which shall mark out from one another the various kinds of Fallacious Evidence, we propose to ourselves an altogether different aim from that of several eminent thinkers, who have given, under the name of Political or other Fallacies, a mere enumeration of a certain number of erroneous opinions; false general propositions which happen to be often met with…. Logic is not concerned with the false opinions which people happen to entertain, but with the manner in which they come to entertain them.15

Joe Nickell

The person who thinks he can't be fooled has just fooled himself.16

Charles Sanders Peirce

Few persons care to study logic, because everybody conceives himself to be proficient enough in the art of reasoning already. But I observe that this satisfaction is limited to one's own ratiocination, and does not extend to that of other men.17

Bertrand Russell

Logical errors are, I think, of greater practical importance than many people believe; they enable their perpetrators to hold the comfortable opinion on every subject in turn.18

Marcello Truzzi

An extraordinary claim requires extraordinary proof.19

Leon Wieseltier

Do not look down on nonsense. Nonsense comes to power. Nonsense murders millions. It prospers if we are too exquisite, too intellectually respectable, to bother with it.20

Christian Wolff

…[L]east of all can we advance, that the study and practice of Logic are unnecessary. For when a man has not a distinct knowledge of the Rules by which the understanding is directed, he may err in the use of his natural powers; as we have instances of those illogical reasonings, by which learned men are sometimes led into error.21


  1. Jeremy Bentham, Bentham's Handbook of Political Fallacies (Apollo Editions, 1971), p. 246.
  2. George Berkeley, Alciphron or: The Minute Philosopher, Fifth Dialogue. Via: David Marans, Logic Gallery: Ancient Greece to the 21st Century.
  3. Lewis Carroll, Symbolic Logic, Part 1: Elementary (Fourth Edition) (Dover, 1958), p. xvii.
  4. Robert Ellis, et al., Charlie Chan at the Race Track (1936). Charlie Chan is a fictional character, in case you don't know.
  5. Augustus De Morgan, Syllabus of a Proposed System of Logic (1860), p. 9. Thanks to David Marans for this quote.
  6. Epictetus, Discourses, translated by Elizabeth Carter & Thomas Wentworth Higginson, Book 2, Chapter 25.
  7. David Hackett Fischer, Historians' Fallacies: Toward a Logic of Historical Thought (Harper & Row, 1970), p. 306.
  8. Steve Pyke, Philosophers (1996).
  9. Laurence J. Peter, Peter's Quotations: Ideas for Our Time (1977), p. 425.
  10. Christopher Hitchens, God is Not Great (2007), p. 150.
  11. Thomas Henry Huxley, The Crayfish, Chapter 1.
  12. Thomas Jefferson, From Thomas Jefferson to David Harding, 20 April 1824, National Archives.
  13. Joseph Joubert, Pensées of Joubert, selected & translated by Henry Attwell (1896), p. 35.
  14. Translation:
    The mind has its illusions as the sense of sight; and in the same manner that the sense of feeling corrects the latter, reflection and calculation correct the former.

    Source: Pierre Simon, Marquis de Laplace, A Philosophical Essay on Probabilities (Dover, 1952), p. 160.

  15. John Stuart Mill, A System of Logic, Book V, Chapter II, § 1.
  16. David Grossberg, "Joe Nickell, Autograph Detective", Autograph Collector, April/May 2007, pp. 78-80.
  17. Charles Sanders Peirce, "The Fixation of Belief", Popular Science Monthly 12 (November 1877), pp. 1-15.
  18. Bertrand Russell, A History of Western Philosophy (Book-of-the-Month Club, 1995), p. 93.
  19. Marcello Truzzi, "On the Extraordinary: An Attempt at Clarification", Zetetic Scholar: An Independent Scientific Review of Claims of Anomalies and the Paranormal, Vol. 1, No. 1 (1978), p. 11. This not-so extraordinary claim was popularized by Carl Sagan in the form: "Extraordinary claims require extraordinary evidence." See, for instance: Carl Sagan, Broca's Brain: Reflections on the Romance of Science (1980) p. 73.
  20. Leon Wieseltier, "Reason and the Republic of Opinion", New Republic, 11/11/2014.
  21. Christian Wolff, Logic (1770), p. 216. Thanks to David Marans for calling my attention to this quote.