Sixteen Philosophical Quotes on Skepticism (With References)

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This page contains a collection of philosophical quotes on skepticism, arranged in roughly chronological order. These quotes are all genuine and details about the author, book, chapter number, and translation are included where applicable. Without further ado, here are sixteen philosophical quotes on skepticism:


If a man believe that nothing is known, he knows not whether this even can be known, since he admits he knows nothing. I will therefore decline to argue the case against him who places himself with head where his feet should be.

– Lucretius, On the Nature of Things, IV, trans. H. A. J. Munro


I shall then suppose, not that God who is supremely good and the fountain of truth, but some evil genius not less powerful than deceitful, has employed his whole energies in deceiving me; I shall consider that the heavens, the earth, colours, figures, sound, and all other external things are nought but the illusions and dreams of which this genius has availed himself in order to lay traps for my credulity; I shall consider myself as having no hands, no eyes, no flesh, no blood, nor any senses, yet falsely believing myself to possess all these things; I shall remain obstinately attached to this idea, and if by this means it is not in my power to arrive at the knowledge of any truth, I may at least do what is in my power [i.e. suspend my judgment], and with firm purpose avoid giving credence to any false thing, or being imposed upon by this arch deceiver, however powerful and deceptive he may be.

– René Descartes, Meditations on First Philosophy, I, trans. Elizabeth S. Haldane


But [if] there is some deceiver or other, very powerful and very cunning, who ever employs his ingenuity in deceiving me. Then without doubt I exist also if he deceives me, and let him deceive me as much as he will, he can never cause me to be nothing so long as I think that I am something. So that after having reflected well and carefully examined all things, we must come to the definite conclusion that this proposition: I am, I exist, is necessarily true each time that I pronounce it, or that I mentally conceive it.

– René Descartes, Meditations on First Philosophy, II, trans. Elizabeth S. Haldane


I suppose, then, that all the things that I see are false; I persuade myself that nothing has ever existed of all that my fallacious memory represents to me. I consider that I possess no senses; I imagine that body, figure, extension, movement and place are but the fictions of my mind. What, then, can be esteemed as true? Perhaps nothing at all, unless that there is nothing in the world that is certain.

– René Descartes, Meditations on First Philosophy, II, trans. Elizabeth S. Haldane


What astonishes me most is to see that all the world is not astonished at its own weakness. Men act seriously, and each follows his own mode of life, not because it is in fact good to follow since it is the custom, but as if each man knew certainly where reason and justice are. They find themselves continually deceived, and by a comical humility think it is their own fault, and not that of the art which they claim always to possess. But it is well there are so many such people in the world, who are not sceptics for the glory of scepticism, in order to show that man is quite capable of the most extravagant opinions, since he is capable of believing that he is not in a state of natural and inevitable weakness, but, on the contrary, of natural wisdom. Nothing fortifies scepticism more than that there are some who are not sceptics; if all were so, they would be wrong.

– Blaise Pascal, Pensées, VI, 374, trans. W. F. Trotter


How vain . . . it is to expect demonstration and certainty in things not capable of it; and refuse assent to very rational propositions, and act contrary to very plain and clear truths, because they cannot be made out so evident, as to surmount every the least (I will not say reason, but) pretence of doubting. He that, in the ordinary affairs of life, would admit of nothing but direct plain demonstration, would be sure of nothing in this world, but of perishing quickly.

– John Locke, An Essay Concerning Human Understanding, Bk. IV, XI,10


If we will disbelieve everything, because we cannot certainly know all things, we shall do muchwhat as wisely as he who would not use his legs, but sit still and perish, because he had no wings to fly.

– John Locke, An Essay Concerning Human Understanding, Intro.


The same principles which at first view lead to scepticism, pursued to a certain point bring men back to common sense.

– George Berkeley, Three Dialogues between Hylas and Philonous, 3


To what purpose is it for philosophy to decide against common sense in this or any other matter? The belief of a material world is older, and of more authority, than any principles of philosophy. It declines the tribunal of reason, and laughs at all the artillery of the logician.

– Thomas Reid, An Inquiry into the Human Mind, VII


Thus the sceptic still continues to reason and believe, even though be asserts, that he cannot defend his reason by reason; and by the same rule he must assent to the principle concerning the existence of body, though he cannot pretend by any arguments of philosophy to maintain its veracity. Nature has not left this to his choice, and has doubtless, esteemed it an affair of too great importance to be trusted to our uncertain reasonings and speculations. We may well ask, What causes induce us to believe in the existence of body? but it is in vain to ask, Whether there be body or not? That is a point, which we must take for granted in all our reasonings.

– David Hume, A Treatise of Human Nature, Bk. I, IV, 2


Most fortunately it happens, that since reason is incapable of dispelling these clouds [of scepticism], nature herself suffices to that purpose, and cures me of this philosophical melancholy and delirium, either by relaxing this bent of mind, or by some avocation, and lively impression of my senses, which obliterate all these chimeras. I dine, I play a game of backgammon, I converse, and am merry with my friends; and when after three or four hours’ amusement, I would return to these speculations, they appear so cold, and strained, and ridiculous, that I cannot find in my heart to enter into them any farther. Here then I find myself absolutely and necessarily determined to live, and talk, and act like other people in the common affairs of life.

– David Hume, A Treatise of Human Nature, Bk. I, IV, 7


The Cartesian doubt . . . were it ever possible to be attained by any human creature (as it plainly is not) would be entirely incurable; and no reasoning could ever bring us to a state of assurance and conviction upon any subject.

– David Hume, An Enquiry Concerning Human Understanding, XII, 116


For here is the chief and most confounding objection to excessive scepticism, that no durable good can ever result from it; while it remains in its full force and vigour. We need only ask such a sceptic, What his meaning is? And what he proposes by all these curious researches? He is immediately at a loss, and knows not what to answer. . . . a Pyrrhonian [skeptic] cannot expect, that his philosophy will have any constant influence on the mind: or if it had, that its influence would be beneficial to society. On the contrary, he must acknowledge, if he will acknowledge anything, that all human life must perish, were his principles universally and steadily to prevail. All discourse, all action would immediately cease; and men remain in a total lethargy, till the necessities of nature, unsatisfied, put an end to their miserable existence. It is true; so fatal an event is very little to be dreaded. Nature is always too strong for principle. And though a Pyrrhonian may throw himself or others into a momentary amazement and confusion by his profound reasonings; the first and most trivial event in life will put to flight all his doubts and scruples, and leave him the same, in every point of action and speculation, with the philosophers of every other sect, or with those who never concerned themselves in any philosophical researches. When he awakes from his dream, he will be the first to join in the laugh against himself, and to confess, that all his objections are mere amusement, and can have no other tendency than to show the whimsical condition of mankind, who must act and reason and believe; though they are not able, by their most diligent enquiry, to satisfy themselves concerning the foundation of these operations, or to remove the objections, which may be raised against them.

– David Hume, An Enquiry Concerning Human Understanding, XII, 126-128


There is, indeed, a more mitigated scepticism or academical philosophy, which may be both durable and useful, and which may, in part, be the result of this Pyrrhonism, or excessive scepticism, when its undistinguished doubts are, in some measure, corrected by common sense and reflection. The greater part of mankind are naturally apt to be affirmative and dogmatical in their opinions; and while they see objects only on one side, and have no idea of any counterpoising argument, they throw themselves precipitately into the principles, to which they are inclined; nor have they any indulgence for those who entertain opposite sentiments. . . . But could such dogmatical reasoners become sensible of the strange infirmities of human understanding, even in its most perfect state, and when most accurate and cautious in its determinations; such a reflection would naturally inspire them with more modesty and reserve, and diminish their fond opinion of themselves, and their prejudice against antagonists. The illiterate may reflect on the disposition of the learned, who, amidst all the advantages of study and reflection, are commonly still diffident in their determinations: and if any of the learned be inclined, from their natural temper, to haughtiness and obstinacy, a small tincture of Pyrrhonism might abate their pride, by showing them, that the few advantages, which they may have attained over their fellows, are but inconsiderable, if compared with the universal perplexity and confusion, which is inherent in human nature. In general, there is a degree of doubt, and caution, and modesty, which, in all kinds of scrutiny and decision, ought for ever to accompany a just reasoner.

– David Hume, An Enquiry Concerning Human Understanding, XII, 129


What danger can ever come from ingenious reasoning and enquiry? The worst speculative skeptic ever I knew was a much better man than the best superstitious devotee and bigot.

– David Hume, Letter to Gilber Elliot, (Mar 10. 1751)


Philosophers of very diverse stripes propose that philosophy shall take its start from one or another state of mind in which no man, least of all a beginner in philosophy, actually is. One proposes that you shall begin by doubting everything, and says that there is only one thing that you cannot doubt, as if doubting were “as easy as lying.” Another proposes that we should begin by observing “the first impressions of sense,” for getting that our very percepts are the results of cognitive elaboration. But in truth, there is but one state of mind from which you can “set out,” namely, the very state of mind in which you actually find yourself at the time you do “set out,” a state in which you are laden with an immense mass of cognition already formed, of which you cannot divest yourself if you would; and who knows whether, if you could, you would not have made all knowledge impossible to yourself? Do you call it doubting to write down on a piece of paper that you doubt? If so, doubt has nothing to do with any serious business. But do not make believe; if pedantry has not eaten all the reality out of you, recognise, as you must, that there is much that you do not doubt, in the least. Now that which you do not at all doubt, you must and do regard as infallible, absolute truth.

– C. S. Peirce, What Pragmatism Is


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