Philosophy of knowledge: philosopher and scientist quotes

This post is a list of quotes from scientists and philosophers about the philosophy of knowledge. I tried to find quotes that provide an abstract view about knowledge. There is one quote per person and they are ordered chronologically by date of birth of the person. The picture above is a detail from the painting Girl With Pearl Earring (1665) by Johannes Vemeer.

Ancient History

Hesiod (around 700 BC, poet):
"It is best to do things systematically, since we are only human, and disorder is our worst enemy." (Brainy Quotes)

Pythagoras (570-495 BC, mathematician):
"There is geometry in the humming of the strings, there is music in the spacing of the spheres." (Wikiquote)

Socrates (470-399 BC, philosopher):
"The body is a source of endless trouble to us by reason of the mere requirement of food; and is also liable to diseases which overtake and impede us in the search after truth: and by filling us so full of loves, and lusts, and fears, and fancies, and idols, and every sort of folly, prevents our ever having, as people say, so much as a thought." (Phaedo)

Democritus (460-370 BC, philosopher):
"We know nothing accurately in reality, but [only] as it changes according to the bodily condition, and the constitution of those things that flow upon [the body] and impinge upon it." (Wikiquote)

Euclid (435-365 BC, mathematician):
"The laws of nature are but the mathematical thoughts of God." (Elements)

Plato (427-347 BC, philosopher):
"Rhetoric, it seems, is a producer of persuasion for belief, not for instruction in the matter of right and wrong … And so the rhetorician's business is not to instruct a law court or a public meeting in matters of right and wrong, but only to make them believe." (Wikiquote)

Aristotle (384-322 BC, philosopher):
"The natural way of doing this (seeking scientific knowledge or explanation of fact) is to start from the things which are more knowable and obvious to us and proceed towards those which are clearer and more knowable by nature; for the same things are not 'knowable relatively to us' and 'knowable' without qualification. So in the present inquiry we must follow this method and advance from what is more obscure by nature, but clearer to us, towards what is more clear and more knowable by nature. Now what is to us plain and obvious at first is rather confused masses, the elements and principles of which became known to us by later analysis." (Physics)

Epicurus (341-270 BC, philosopher):
"We must consider both the ultimate end and all clear sensory evidence, to which we refer our opinions; for otherwise everything will be full of uncertainty and confusion." (Sovereign Maxims)

Herophilos (335-280 BC, physician):
"When health is absent, wisdom cannot reveal itself, art cannot become manifest, strength cannot be exerted, wealth is useless, and reason is powerless." (AZ Quotes)

Archimedes (287-212 BC, mathematics):
"How many theorems in geometry which have seemed at first impracticable are in time successfully worked out!" (Wikiquote)

Year 0

Ptolemy (100-170 CE, mathematician):
"We consider it a good principle to explain the phenomena by the simplest hypothesis possible." (Wikiquote)

Galen (129-200 CE, physician):
"It would be better, I think, for the man who really seeks the truth not to ask what the poets say; rather, he should first learn the method of finding the scientific premises that I discussed in the second book; then he should train and exercise himself in this method; and when his training is sufficiently advanced, then, as he approaches each particular problem, he should enquire into the premise needed for proving it, which premise he should take from simple sense-perception, which from experience, whether drawn from life or from the arts, which from the truths clearly apprehended by the mind, in order to draw out from them the desired conclusion." (2nd cen. CE, On the Doctrines of Hippocrates and Plato)

Boethius (480-524 CE, philosopher):
"By first recognizing false goods, you begin to escape the burden of their influence; then afterwards true goods may gain possession of your spirit." (The Consolation of Philosophy)

Ibn al-Haytham (965-1040 CE, mathematician):
"The seeker after the truth is not one who studies the writings of the ancients and, following his natural disposition, puts his trust in them, but rather the one who suspects his faith in them and questions what he gathers from them, the one who submits to argument and demonstration, and not to the sayings of a human being whose nature is fraught with all kinds of imperfection and deficiency. Thus the duty of the man who investigates the writings of scientists, if learning the truth is his goal, is to make himself an enemy of all that he reads, and, applying his mind to the core and margins of its content, attack it from every side. He should also suspect himself as he performs his critical examination of it, so that he may avoid falling into either prejudice or leniency." (Wikiquote)

Al-Biruni (973-1048 CE, philosopher):
"Once a sage asked why scholars always flock to the doors of the rich, whilst the rich are not inclined to call at the doors of scholars. 'The scholars' he answered , 'are well aware of the use of money, but the rich are ignorant of the nobility of science'."(Wikiquote)

Avicenna (980-1037 CE, philosopher):
"The knowledge of anything, since all things have causes, is not acquired or complete unless it is known by its causes." (1020, On Medicine)

1000

Robert Grosseteste (1175-1253, philosopher):
"The consideration of lines, angles and figures is of the greatest utility since it is impossible for natural philosophy to be known without them... All causes of natural effects have to be given through lines, angles and figures, for otherwise it is impossible for the reason why (propter quid) to be known in them." (De Lineas, Anguilis et Figuris)

Albertus Magnus (1200-1280, philosopher):
"Nature must be the foundation and model of science; thus Art works according to Nature in everything it can. Therefore, it is necessary that the Artist follows Nature and operates according to her." (De Vegetabilibus)

Roger Bacon (1219-1292, philosopher):
"Reasoning draws a conclusion and makes us grant the conclusion, but does not make the conclusion certain, nor does it remove doubt so that the mind may rest on the intuition of truth, unless the mind discovers it by the path of experience." (1267, Opus Majus)

Thomas Aquinas (1225-1274, philosopher):
"The greatness of the human being consists in this: that it is capable of the universe." (Wikiquote)

William of Ockham (1287-1347, philosopher):
"It is pointless to do with more what can be done with fewer."

Ibn Khaldun (1332-1406, historian):
"Eventually, Aristotle appeared among the Greeks. He improved the methods of logic and systematized its problems and details. He assigned to logic its proper place as the first philosophical discipline and the introduction to philosophy. Therefore he is called the 'First Teacher'." (1377, Muqaddimah)

Leonardo da Vinci (1452-1519, polymath):
"There is no certainty in sciences where one of the mathematical sciences cannot be applied, or which are not in relation with these mathematics." (Notebooks of Leonardo da Vinci)

Niccolo Machiavelli (1469-1527, philosopher):
"A prudent man should always follow in the path trodden by great men and imitate those who are most excellent." (1513, The Prince)

Nicolaus Copernicus (1473-1543, astronomer):
"When, therefore, I had long considered this uncertainty of traditional mathematics, it began to weary me that no more definite explanation of the movement of the world-machine established in our behalf by the best and most systematic builder of all, existed among the philosophers who had studied so exactly in other respects the minutest details in regard to the sphere." (Preface Letter to Pope Paul III)

Michelangelo (1475-1564, artist):
"Every beauty which is seen here below by persons of perception resembles more than anything else that celestial source from which we all are come."

1500

Andreas Vesalius (1514-1564, physician):
"I am not accustomed to saying anything with certainty after only one or two observations." (De Humani Corporis Fabrica Libri Septem, 1543)

Francis Bacon (1561-1626, philosopher):
"Truth emerges more readily from error than from confusion." (1920, Novum Organum)

Galileo Galilei (1564-1642, astronomer):
"Philosophy is written in this grand book, which stands continually open before our eyes (I say the 'Universe'), but can not be understood without first learning to comprehend the language and know the characters as it is written. It is written in mathematical language, and its characters are triangles, circles and other geometric figures, without which it is impossible to humanly understand a word; without these one is wandering in a dark labyrinth." (1923, Il Saggiatore)

Johannes Kepler (1571-1630, astronomer):
"Geometry is one and eternal shining in the mind of God. That share in it accorded to humans is one of the reasons that humanity is the image of God." (1618, Harmonics Mundi)

William Harvey (1578-1657, physician):
"As art is a habit with reference to things to be done, so is science a habit in respect to things to be known." (1651, De Generatione Animalium)

Thomas Hobbes (1588-1679, philosopher):
"'Understanding' being nothing else, but conception caused by speech." (1651, The Leviathan)

Rene Descartes (1596-1650, philosopher):
"Each problem that I solved became a rule, which served afterwards to solve other problems." (Brainy Quote)

1600

Rembrandt (1606-1669, artist):
"Try to put well in practice what you already know; and in so doing, you will in good time, discover the hidden things which you now inquire about. Practice what you know, and it will help to make clear what now you do not know." (1908, A Dictionary of Thoughts)

Blaise Pascal (1623-1662, mathematician):
"Logic has borrowed, perhaps, the rules of geometry, without comprehending their force... it does not thence follow that they have entered into the spirit of geometry, and I should be greatly averse... to placing them on a level with that science that teaches the true method of directing reason." (The Art of Persuasion)

Christian Huygens (1629-1695, mathematician):
"There are many degrees of Probable, some nearer Truth than others, in the determining of which lies the chief exercise of our Judgment." (1695, Cosmotheoros)

Baruch Spinoza (1632-1677, philosopher):
"A definition, if it is to be called perfect, must explain the inmost essence of a thing, and must take care not to substitute for this any of its properties." (1662, On the Improvement of Understanding)

Antony van Leeuwenhoek (1632-1732, biologist):
"A man has always to be busy with his thoughts if anything is to be accomplished." (Brainy Quote)

John Locke (1632-1704, philosopher):
"This is that which I think great readers are apt to be mistaken in; those who have read of everything, are thought to understand everything too; but it is not always so. Reading furnishes the mind only with materials of knowledge; it is thinking that makes what we read ours. We are of the ruminating kind, and it is not enough to cram ourselves with a great load of collections ; unless we chew them over again, they will not give us strength and nourishment." (Hand Book : Caution and Counsels)

Thomas Burnet (1635-1715, philosopher):
"I can easily believe, that there are more invisible than visible beings in the universe." (Archaelogiae philosophicae: sive, doctrina antiqua de rerum originibus, libri duo)

Robert Hooke (1635-1703, inventor):
"The truth is, the Science of Nature has been already too long made only a work of the Brain and the Fancy: It is now high time that it should return to the plainness and soundness of Observations on material and obvious things." (AZ Quotes)

Isaac Newton (1642-1727, physicist):
"I do not know what I may appear to the world, but to myself I seem to have been only like a boy playing on the sea-shore, and diverting myself in now and then finding a smoother pebble or a prettier shell than ordinary, whilst the great ocean of truth lay all undiscovered before me." (1855, Memoirs of the Life, Writings, and Discoveries of Sir Isaac Newton)

Gottfried Leibniz (1646-1716, mathematician):
"Only geometry can hand us the thread (which will lead us through) the labyrinth of the continuum’s composition, the maximum and the minimum, the infinitesimal and the infinite; and no one will arrive at a truly solid metaphysic except he who has passed through this (labyrinth)." (1676, Dissertatio Exoterica De Statu Praesenti et Incrementis Novissimis Deque Usu Geometriae)

George Berkeley (1685-1753, philosopher):
"Abstract terms (however useful they may be in argument) should be discarded in meditation, and the mind should be fixed on the particular and the concrete, that is, on the things themselves." (1721, De Motu)

Montesquieu (1689-1755, philosopher):
"Nothing is a greater obstacle to our progress in knowledge, then a bad performance of a celebrated author; because, before we instruct we must begin with undeceiving." (1748, The Spirit of the Laws)

Francis Hutcheson (1694-1746, philosopher):
"Whoever voluntarily undertakes the necessary office of rearing and educating, obtains the parental power without generation." (1755, A System Of Moral Philosophy)

Voltaire (1694-1778, writer):
"Doubt is not a pleasant condition, but certainty is an absurd one."

1700

Leonhard Euler (1707-1783, mathematician):
"Since the fabric of the universe is most perfect and the work of a most wise Creator, nothing at all takes place in the universe in which some rule of maximum or minimum does not appear … there is absolutely no doubt that every affect in the universe can be explained satisfactorily from final causes, by the aid of the method of maxima and minima, as it can be from the effective causes themselves … Of course, when the effective causes are too obscure, but the final causes are readily ascertained, the problem is commonly solved by the indirect method..." (Wikiquote)

George-Louis Leclerc, Comte de Buffon (1707-1788, philosopher):
"Genius is nothing else than a great aptitude for patience." (La visite à Buffon, ou Voyage à Montbard, 1790)

David Hume (1711-1776, philosopher):
"There is nothing in any object, considered in itself, which can afford us a reason for drawing a conclusion beyond it, [...] even after the observation of the frequent or constant conjunction of objects, we have no reason to draw any inference concerning any object beyond those of which we have had experience." (1739, A Treatise of Human Nature)

Mikhail Lomonosov (1711-1765, chemist):
"Nature uncovers the inner secrets of nature in two ways: one by the force of bodies operating outside it; the other by the very movements of its innards. The external actions are strong winds, rains, river currents, sea waves, ice, forest fires, floods; there is only one internal force-earthquake." (AZ Quotes)

Jean-Jacques Rousseau (1712-1778, philosopher):
"Our island is this earth; and the most striking object we behold is the sun. As soon as we pass beyond our immediate surroundings, one or both of these must meet our eye. Thus the philosophy of most savage races is mainly directed to imaginary divisions of the earth or to the divinity of the sun." (1762, On Education)

Denis Diderot (1713-1784):
"In order to shake a hypothesis, it is sometimes not necessary to do anything more than push it as far as it will go." (1753, On the Interpretation of Nature)

Adam Smith (1723-1790, philosopher):
"The difference between the most dissimilar characters, between a philosopher and a common street porter, for example, seems to arise not so much from nature, as from habit, custom, and education." (1776, The Wealth of Nations)

Immanuel Kant (1724-1804, philosopher):
"Reason in a creature is a faculty of widening the rules and purposes of the use of all its powers far beyond natural instinct; it acknowledges no limits to its projects. Reason itself does not work instinctively, but requires trial, practice, and instruction in order gradually to progress from one level of insight to another." (1784, Idea for a Universal History from a Cosmopolitan Point of View)

Joseph Black (1728-1799, chemist):
"A nice adaptation of conditions will make almost any hypothesis agree with the phenomena. This will please the imagination but does not advance our knowledge." (AZ Quotes)

Torbern Bergman (1735-1784, chemist):
"A scientist strives to understand the work of Nature. But with our insufficient talents as scientists, we do not hit upon the truth all at once. We must content ourselves with tracking it down, enveloped in considerable darkness, which leads us to make new mistakes and errors. By diligent examination, we may at length little by little peel off the thickest layers, but we seldom get the core quite free, so that finally we have to be satisfied with a little incomplete knowledge." (Today in Science History)

Moses Mendelssohn (1729-1786, philosopher):
"The analysis of concepts is for the understanding nothing more than what the magnifying glass is for sight." (Brainy Quote)

James Watt (1736-1819, inventor):
"I can think of nothing else than this machine." (Wikiquote)

Joseph Louis Lagrange (1736-1813, mathematician):
"An ancient writer said that arithmetic and geometry are the wings of mathematics; I believe one can say without speaking metaphorically that these two sciences are the foundation and essence of all the sciences which deal with quantity. Not only are they the foundation, they are also, as it were, the capstones; for, whenever a result has been arrived at, in order to use that result, it is necessary to translate it into numbers or into lines; to translate it into numbers requires the aid of arithmetic, to translate it into lines necessitates the use of geometry." (Wikiquote)

Antoine Lavoisier (1743-1794, chemist):
"The art of concluding from experience and observation consists in evaluating probabilities, in estimating if they are high or numerous enough to constitute proof. This type of calculation is more complicated and more difficult than one might think. It demands a great sagacity generally above the power of common people." (1784, Rapport des commissaires chargés par le roi de l'examen du magnétisme animal)

Alessandro Volta (1745-1827, physicist):
"The language of experiment is more authoritative than any reasoning: facts can destroy our ratiocination - not vice versa." (Today in Science History)

Pierre-Simon Laplace (1749-1827, mathematician):
"Life's most important questions are, for the most part, nothing but probability problems." (Wikiquote)

Wolfgang Amadeus Mozart (1756-1791, musician):
I pay no attention whatever to anybody's praise or blame. I simply follow my own feelings. (Brainy Quote)

Georges Cuvier (1769-1832, naturalist):
"It is evident that one cannot say anything demonstrable about the problem before having resolved these preliminary questions, and yet we hardly possess the necessary information to solve some of them." (1796, stated before the National Institute of Sciences and Arts in Paris)

Alexander von Humboldt (1769-1859, geographer):
"There are three stages of scientific discovery: first people deny it is true; then they deny it is important; finally they credit the wrong person." (Good Reads)

Georg Wilhelm Friedrich Hegel (1770-1831, philosopher):
"Reading the morning newspaper is the realist's morning prayer. One orients one's attitude toward the world either by God or by what the world is. The former gives as much security as the latter, in that one knows how one stands." (Miscellaneous writings of G.W.F. Hegel by Jon Bartley Stewart)

Hans Christian Orsted (1771-1851, physicist):
"The agreement of this law with nature will be better seen by the repetition of experiments than by a long explanation." (1820, Experiments on the Effect of a Current of Electricity on the Magnetic Needle, Annals of Philosophy)

Amedeo Avogadro (1776-1856, chemist):
"It must ... be admitted that very simple relations ... exist between the volumes of gaseous substances and the numbers of simple or compound molecules which form them." (Today in Science)

Carl Friedrich Gauss (1777-1809, mathematician):
"I mean the word proof not in the sense of the lawyers, who set two half proofs equal to a whole one, but in the sense of a mathematician, where ½ proof = 0, and it is demanded for proof that every doubt becomes impossible." (1826, Letter to Heinrich Wilhelm Matthias Olbers)

Carl von Clausewitz (1780-1831, philosopher):
"Any complex activity, if it is to be carried on with any degree of virtuosity, calls for appropriate gifts of intellect and temperament. If they are outstanding and reveal themselves in exceptional achievements, their possessor is called a 'genius'." (1832, On War)

Jeremy Bentham (1784-1832, philosopher):
"He who thinks and thinks for himself, will always have a claim to thanks; it is no matter whether it be right or wrong, so as it be explicit. If it is right, it will serve as a guide to direct; if wrong, as a beacon to warn." (Brainy Quote)

Adam Sedgwick (1785-1873, geologist):
"As a system of philosophy it is not like the Tower of Babel, so daring its high aim as to seek a shelter against God's anger; but it is like a pyramid poised on its apex." (Brainy Quote)

Louis Daguerre (1787-1851, inventor):
"The daguerreotype is not merely an instrument which serves to draw Nature; on the contrary it is a chemical and physical process which gives her the power to reproduce herself." (Art Quotes)

Arthur Schopenhauer (1788-1860, philosopher):
"Talent hits a target no one else can hit; Genius hits a target no one else can see." (1819, The World as Will and Representation)

Michael Faraday (1791-1867, physicist):
"I was at first almost frightened when I saw such mathematical force made to bear upon the subject, and then wondered to see that the subject stood it so well." (1857, Letter to James Clerk Maxwell)

Charles Babbage (1791-1871, inventor):
"It is therefore not unreasonable to suppose that some portion of the neglect of science in England, may be attributed to the system of education we pursue. A young man passes from our public schools to the universities, ignorant of almost every branch of useful knowledge; and at these latter establishments … classical and mathematical pursuits are nearly the sole objects proposed to the student's ambition." (1830, Reflections on the Decline of Science in England, and on Some of its Causes)

John Herschel (1792-1871, mathematician):
"To ascend to the origin of things and speculate on the creation, is not the business of the natural philosopher. An humbler field is sufficient for him in the endeavor to discover, as far as our faculties will permit; what are these primary qualities impressed on matter, and to discover the spirit of the laws of nature."  (1831, A Preliminary Discourse on the Study of Natural Philosophy)

William Whewell (1794-1866, philosopher):
"Fundamental ideas are not a consequence of experience, but a result of the particular constitution and activity of the mind, which is independent of all experience in its origin, though constantly combined with experience in its exercise." (Brainy Quote)

Jules Michelet (1798-1874, historian):
"You are one of the forces of nature." (Brainy Quotes)

1800

Friedrich Wohler (1800-1882, chemist):

"Organic chemistry just now is enough to drive one mad. It gives me the impression of a primeval forest full of the most remarkable things, a monstrous and boundless thicket, with no way of escape, into which one may well dread to enter." (Today in Science History)

Henry Fox Talbot (1800-1877, inventor):
"One advantage of the discovery of the Photographic Art will be, that it will enable us to introduce into our pictures a multitude of minute details which add to the truth and reality of the representation, but which no artist would take the trouble to faithfully copy from nature." (AZ Quotes)

John Stuart Mill (1806-1873, philosopher):
"Persons of genius, it is true, are, and are always likely to be, a small minority; but in order to have them, it is necessary to preserve the soil in which they grow. Genius can only breathe freely in an atmosphere of freedom." (1859, On Liberty)

Charles Darwin (1809-1882, biologist):
"I have deeply regretted that I did not proceed far enough at least to understand something of the great leading principles of mathematics, for men thus endowed seem to have an extra sense." (1887, The Life and Letters of Charles Darwin)

Claude Bernard (1813-1878, physician):
"What really should be done, instead of gathering facts empirically, is to study them more accurately, each in its special determinism." (1865, Introduction à l'Étude de la Médecine Expérimentale)

Henry David Thoreau (1817-1862, philosopher):
"I find it so difficult to dispose of the few facts which to me are significant, that I hesitate to burden my attention with those which are insignificant, which only a divine mind could illustrate. Such is, for the most part, the news in newspapers and conversation. It is important to preserve the mind's chastity in this respect." (1863, Life with Principles)

Herbert Spencer (1820-1903, sociologist):
"How often misused words generate misleading thoughts." (Brainy Quote)

Fyodor Dostoyevsky (1821-1881, writer):
"Oh, how hard it is to be the only one who knows the truth! But they won't understand that. No, they won't understand it." (1877, The Dream of a Ridiculous Man)

Louis Pasteur (1822-1895, chemist):
"There does not exist a category of science to which one can give the name applied science. There are sciences and the applications of science, bound together as the fruit of the tree which bears it." (1871, Revue Scientifique)

Thomas Henry Huxley (1825-1895, biologist):
"The method of scientific investigation is nothing but the expression of the necessary mode of working of the human mind. (1863, Our Knowledge of the Causes of the Phenomena of Organic Nature)

Bernhard Riemann (1826-1866, mathematician):
"As is known, scientific physics dates its existence from the discovery of the differential calculus. Only when it was learned how to follow continuously the course of natural events, attempts, to construct by means of abstract conceptions the connection between phenomena, met with success." (Wikiquote)

James Clerk Maxwell (1831-1879, physicist):
"Mathematicians may flatter themselves that they possess new ideas which mere human language is yet unable to express. Let them make the effort to express these ideas in appropriate words without the aid of symbols, and if they succeed they will not only lay us laymen under a lasting obligation, but we venture to say, they will find themselves very much enlightened during the process, and will even be doubtful whether the ideas as expressed in symbols had ever quite found their way out of the equations of their minds." (1864, A Dynamical Theory of the Electromagnetic Field)

Dmitri Mendeleev (1834-1907, chemist):
"I wish to establish some sort of system not guided by chance but by some sort of definite and exact principle." (Wikiquote)

Charles Sanders Peirce (1839-1914, philosopher):
"Few persons care to study logic, because everybody conceives himself to be proficient enough in the art of reasoning already." (1877, Illustrations of the Logic of Science)

William James (1842-1910, psychologist):
"All our scientific and philosophic ideals are altars to unknown gods." (1884, Lecture at the Harvard Divinity School)

Friedrich Nietzsche (1844-1900, philosopher):
"Art is the supreme task and the truly metaphysical activity in this life." (1889, Preface to Richard Wagner)

Thomas Edison (1847-1931, inventor):
"During all those years of experimentation and research, I never once made a discovery. All my work was deductive, and the results I achieved were those of invention, pure and simple. I would construct a theory and work on its lines until I found it was untenable. Then it would be discarded at once and another theory evolved. This was the only possible way for me to work out the problem. … I speak without exaggeration when I say that I have constructed 3,000 different theories in connection with the electric light, each one of them reasonable and apparently likely to be true. Yet only in two cases did my experiments prove the truth of my theory. My chief difficulty was in constructing the carbon filament." (1980, Talks with Edison)

Wilhelm Rontgen (1847-1923, physicist):
"I am not a prophet, and I am opposed to prophesying. I am pursuing my investigations, and as fast as my results are verified I shall make them public." (1838, The New Marvel in Photography)

Alexander Graham Bell (1847-1922, inventor):
"You cannot force ideas. Successful ideas are the result of slow growth. Ideas do not reach perfection in a day, no matter how much study is put upon them." (1901, Bell Telephone Talk)

Ivan Pavlov (1849-1936, psychologist):
"Learn, compare, collect the facts!"

Monsignor Georges Lemaitre (1849-1966, astronomer):
"Scientific progress is the discovery of a more and more comprehensive simplicity... The previous successes give us confidence in the future of science: we become more and more conscious of the fact that the universe is cognizable." (Today in Science History)

Santiago Ramón y Cajal (1852-1934, neuroscientist):
"The history of civilization proves beyond doubt just how sterile the repeated attempts of metaphysics to guess at nature' s laws have been. Instead, there is every reason to believe that when the human intellect ignores reality and concentrates within, it can no longer explain the simplest inner workings of life' s machinery or of the world around us." (1897, Advice for a Young Investigator)

Sigmund Freud (1856-1939, psychologist):
"I am actually not at all a man of science, not an observer, not an experimenter, not a thinker. I am by temperament nothing but a conquistador - an adventurer, if you want it translated with - all the curiosity, daring, and tenacity characteristic of a man of this sort." (1900, Letter to Wilhelm Fliess)

Nikola Tesla (1856-1943, physicist):
"I do not think there is any thrill that can go through the human heart like that felt by the inventor as he sees some creation of the brain unfolding to success … Such emotions make a man forget food, sleep, friends, love, everything." (Wikiquote)

Ferdinand de Saussure (1857-1913, linguist):
"Without language, thought is a vague, uncharted nebula." (1916, Cours de linguistique générale)

Alfred Binet (1857-1911, psychologist):
"I wish that one would be persuaded that psychological experiments, especially those on the complex functions, are not improved [by large studies]; the statistical method gives only mediocre results." (Today in Science History)

Max Planck (1858-1947, physician):
"New scientific ideas never spring from a communal body, however organized, but rather from the head of an individually inspired researcher who struggles with his problems in lonely thought and unites all his thought on one single point which is his whole world for the moment." (1936, Address on the 25th anniversary of the Kaiser-Wilhelm Gesellschaft)

Pierre Duhem (1861-1916, physicist):
"A symbol is not, properly speaking, either true or false; it is, rather, something more or less well selected to stand for the reality it represents, and pictures that reality in a more or less precise, or a more or less detailed manner." (1906, The Aim and Structure of Physical Theory)

David Hilbert (1862-1943, mathematician):
"A mathematical problem should be difficult in order to entice us, yet not completely inaccessible, lest it mock at our efforts. It should be to us a guide post on the mazy paths to hidden truths, and ultimately a reminder of our pleasure in the successful solution." (1900, Mathematical Problems)

Max Weber (1864-1920, sociologist):
"Sociology... is a science concerning itself with the interpretive understanding of social action and thereby with a causal explanation of its course and consequences. We shall speak of "action" insofar as the acting individual attaches a subjective meaning to his behavior - be it overt or covert, omission or acquiescence. Action is "social" insofar as its subjective meaning takes account of the behavior of others and is thereby oriented in its course." (Wikiquote)

Wilbur Wright (1867-1912, inventor):
"For some years I have been afflicted with the belief that flight is possible to man. My disease has increased in severity and I feel that it will soon cost me an increased amount of money if not my life. I have been trying to arrange my affairs in such a way that I can devote my entire time for a few months to experiment in this field." (1900, Letter to Octave Chanute)

Marie Currie (1867-1934, physicist):
"I am among those who think that science has great beauty. A scientist in his laboratory is not only a technician: he is also a child placed before natural phenomena which impress him like a fairy tale." (1937, Madame Curie : A Biography)

Edward Titchener (1867-1927, psychologist):
"Knowledge is the product of leisure. The members of a very primitive society have no time to amass knowledge; their days are fully occupied with the provision of the bare necessities of life." (1916, An Outline of Psychology)

Frank Lloyd Wright (1867-1959, architect):
"The scientist has marched in and taken the place of the poet. But one day somebody will find the solution to the problems of the world and remember, it will be a poet, not a scientist." (1959, Wikiquote)

W.E.B. Du Bois (1868-1963, sociologist):
"When you have mastered numbers, you will in fact no longer be reading numbers, any more than you read words when reading books You will be reading meanings." (Brainy Quote)

Alfred Alder (1870-1937, psychologist):
"Meanings are not determined by situations, but we determine ourselves by the meanings we give to situations." (Brainy Quote)

Bertrand Russell (1872-1970, mathematician):
"The scientific attitude of mind involves a sweeping away of all other desires in the interests of the desire to know—it involves suppression of hopes and fears, loves and hates, and the whole subjective emotional life, until we become subdued to the material, able to see it frankly, without preconceptions, without bias, without any wish except to see it as it is, and without any belief that what it is must be determined by some relation, positive or negative, to what we should like it to be, or to what we can easily imagine it to be." (1918, Mysticism and Logic and Other Essays)

Charles Beard (1874-1948, historian):
"When it is dark enough, you can see the stars." (Brainy Quote)

Albert Einstein (1879-1955, physicist):
"How does it happen that a properly endowed natural scientist comes to concern himself with epistemology? Is there not some more valuable work to be done in his specialty? That's what I hear many of my colleagues ask, and I sense it from many more. But I cannot share this sentiment. When I think about the ablest students whom I have encountered in my teaching — that is, those who distinguish themselves by their independence of judgment and not just their quick-wittedness — I can affirm that they had a vigorous interest in epistemology. They happily began discussions about the goals and methods of science, and they showed unequivocally, through tenacious defense of their views, that the subject seemed important to them." (1916, Obituary for physicist and philosopher Ernst Mach)

Franz Kafka (1883-1924, writer):
"I think we ought to read only the kind of books that wound and stab us. If the book we are reading doesn't wake us up with a blow on the head, what are we reading it for? ...we need the books that affect us like a disaster, that grieve us deeply, like the death of someone we loved more than ourselves, like being banished into forests far from everyone, like a suicide. A book must be the axe for the frozen sea inside us." (1904, Letter to Oskar Pollack)

Niels Bohr (1885-1962, physicist):
"We must be clear that when it comes to atoms, language can be used only as in poetry. The poet, too, is not nearly so concerned with describing facts as with creating images and establishing mental connections." (1933, Discussions about Language)

Ernest Rutherford (1871-1937, physicist):
"An alleged scientific discovery has no merit unless it can be explained to a barmaid." (Wikiquote)

Alexis Carrel (1873-1944, biologist):
"All great men are gifted with intuition. They know without reasoning or analysis, what they need to know." (Brainy Quote)

Otto Hahn (1879-1968, chemist):
"Usually, a discovery is not made in the easiest but on a complicated way; the simple cases show up only later." (1962, Vom Radiothor zur Uranspaltung. Eine wissenschaftliche Selbstbiographie)

Alexander Fleming (1881-1955, biologist):
"It is the lone worker who makes the first advance in a subject: the details may be worked out by a team, but the prime idea is due to the enterprise, thought, and perception of an individual." (Wikiquote)

Pablo Picasso (1881-1973, artist):
"I can hardly understand the importance given to the word 'research' in connection with modern painting. In my opinion to search means nothing in painting. To find is the thing. Nobody is interested in following a man who, with his eyes fixed on the ground, spends his life looking for the purse that fortune should put in his path. The one who finds something no matter what it might be, even if his intention were not to search for it, at least arouses our curiosity, if not our admiration." (1923, Picasso Speaks)

Will Durant (1885-1981, philosopher):
"Every science begins as philosophy and ends as art." (1926, The Story of Philosophy)

Srinivasa Ramanujan (1887-1920, mathematician):
"An equation means nothing to me unless it expresses a thought of God." (Wikiquote)

Erwin Schrodinger (1887-1961, physicist):
"Science cannot tell us a word about why music delights us, of why and how an old song can move us to tears." (1958, Mind and Matter)

Ludwig Wittgenstein (1889-1951, philosopher):
"Philosophy aims at the logical clarification of thoughts. Philosophy is not a body of doctrine but an activity. A philosophical work consists essentially of elucidations. Philosophy does not result in 'philosophical propositions', but rather in the clarification of propositions. Without philosophy thoughts are, as it were, cloudy and indistinct: its task is to make them clear and to give them sharp boundaries." (1922, Tractatus Logico-Philosophicus)

Ronald Fisher (1890-1962, statistician):
"After all, it is a common weakness of young authors to put too much into their papers." (Contributions to Mathematical Statistics, 1950)

Zora Neale Hurston (1891-1960, anthropologist):
"Research is formalized curiosity. It is poking and prying with a purpose. It is a seeking that he who wishes may know the cosmic secrets of the world and they that dwell therein." (1942, Dust Tracks on a Road )

Robert Watson-Watt (1892-1973, physicist):
"There is a great deal of emotional satisfaction in the elegant demonstration, in the elegant ordering of facts into theories, and in the still more satisfactory, still more emotionally exciting discovery that the theory is not quite right and has to be worked over again, very much as any other work of art—a painting, a sculpture has to be worked over in the interests of aesthetic perfection. So there is no scientist who is not to some extent worthy of being described as artist or poet." (1948, Scientist and Citizen)

Louis de Broglie (1892-1987, physicist):
"Two seemingly incompatible conceptions can each represent an aspect of the truth … They may serve in turn to represent the facts without ever entering into direct conflict." (1948, Dialectica Volume 2)

Jean Piaget (1896, psychologist):
"To express the same idea in still another way, I think that human knowledge is essentially active." (Brainy Quote)

1900

Howard Aiken (1900-1973, physicist):
"The desire to economize time and mental effort in arithmetical computations, and to eliminate human liability to error is probably as old as the science of arithmetic itself." (1937, Proposed Automatic Calculating Machine)

Wolfgang Pauli (1900-1958, physicist):
"The deepest pleasure in science comes from finding an instantiation, a home, for some deeply felt, deeply held image." (Wikiquote)

Joseph Needham (1900-1995, historian):
"The hierarchy of relations, from the molecular structure of carbon to the equilibrium of the species and ecological whole, will perhaps be the leading idea of the future." (Brainy Quote)

Enrico Fermi (1901-1954, physicist):
"There are two possible outcomes: if the result confirms the hypothesis, then you've made a measurement. If the result is contrary to the hypothesis, then you've made a discovery. (Wikiquote)

Linus Pauling (1901-1944, chemist):
"Facts are the air of scientists. Without them you can never fly." (Brainy Quote)

Werner Heisenberg (1901-1976, physicist):
"Light and matter are both single entities, and the apparent duality arises in the limitations of our language. It is not surprising that our language should be incapable of describing the processes occurring within the atoms, for, as has been remarked, it was invented to describe the experiences of daily life, and these consist only of processes involving exceedingly large numbers of atoms. Furthermore, it is very difficult to modify our language so that it will be able to describe these atomic processes, for words can only describe things of which we can form mental pictures, and this ability, too, is a result of daily experience. Fortunately, mathematics is not subject to this limitation."

Karl Popper (1902-1994, philosopher):
"Bold ideas, unjustified anticipations, and speculative thought, are our only means for interpreting nature: our only organon, our only instrument, for grasping her. And we must hazard them to win our prize. Those among us who are unwilling to expose their ideas to the hazard of refutation do not take part in the scientific game." (1934, The Logic of Scientific Discovery)

Paul Dirac (1902-1984, physicist):
"The interpretation of quantum mechanics has been dealt with by many authors, and I do not want to discuss it here. I want to deal with more fundamental things." (Wikiquote)

Talcott Parsons (1902-1979, philosopher):
"Special emphasis should be laid on this intimate interrelation of general statements about empirical fact with the logical elements and structure of theoretical systems." (Brainy Quote)

George Gamow (1904-1968, physicist):
"It is well known that theoretical physicists cannot handle experimental equipment; it breaks whenever they touch it. [Wolfgang] Pauli was such a good theoretical physicist that something usually broke in the lab whenever he merely stepped across the threshold." (1966, Thirty Years that Shook Physics: The Story of Quantum Theory)

Ernst Mayr (1904-2005):
"Biological classifications have two major objectives: to serve as a basis of biological generalizations in all sort of comparative studies and to serve as a key to an information storage system... Is the classification that is soundest as a basis of generalizations also most convenient for information retrieval? This, indeed, seems to have been true in most cases I have encountered." (Wikiquote)

Gregory Bateson (1904-1980):
"As I see it, the advances in scientific thought come from a combination of loose and strict thinking, and this combination is the most precious tool of science." (1935, Culture Contact and Schismogenesis)

Jean-Paul Sartre (1905-1980, philosopher):
"Imagination is not an empirical or superadded power of consciousness, it is the whole of consciousness as it realizes its freedom." (1936, Imagination: A Psychological Critique)

Rachel Carson (1907-1964, biologist):
"If there is poetry in my book about the sea, it is not because I deliberately put it there, but because no one could write truthfully about the sea and leave out the poetry." (1952,National Book Award for Nonfiction)

Edward Teller (1908-2003, physicist):
"We must learn to live with contradictions, because they lead to deeper and more effective understanding." (1998, Science and Morality)

John Archibald Wheeler (1911-2008, physicist):
"We live on an island surrounded by a sea of ignorance. As our island of knowledge grows, so does the shore of our ignorance." (1922, from Scientific American)

Glenn Seaborg (1912-1999, chemist):
"There is a beauty in discovery. There is mathematics in music, a kinship of science and poetry in the description of nature, and exquisite form in a molecule. Attempts to place different disciplines in different camps are revealed as artificial in the face of the unity of knowledge. All literate men are sustained by the philosopher, the historian, the political analyst, the economist, the scientist, the poet, the artisan and the musician." (1958, Statement upon being appointed as UC Berkeley chancellor)

Mary Leakey (1913-1996, anthropologist):
"Theories come and go, but fundamental data always remain the same." (Brainy Quote)

Charles Townes (1915-2015, physicist):
"In many cases, people who win a Nobel prize, their work slows down after that because of the distractions. Yes, fame is rewarding, but it's a pity if it keeps you from doing the work you are good at." (Brainy Quote)

Thomas Merton (1915-1968, philosopher):
"Art enables us to find ourselves and lose ourselves at the same time." (Brainy Quote)

Richard Feynman (1918-1988, physicist):
"Pure mathematics is just such an abstraction from the real world, and pure mathematics does have a special precise language for dealing with its own special and technical subjects. But this precise language is not precise in any sense if you deal with real objects of the world, and it is only pedantic and quite confusing to use it unless there are some special subtleties which have to be carefully distinguished." (1965, New Textbooks for the New Mathematics)

Frederick Sanger (1918-2013, chemist):
"It is like a voyage of discovery into unknown lands, seeking not for new territory but for new knowledge. It should appeal to those with a good sense of adventure." (Brainy Quote)

Ralph Asher Alpher (1921-2007, phyicist):
"There are two reasons you do science. One is the altruistic feeling that maybe you can contribute to mankind's store of knowledge about the world. The other and more personal thing is you want the approbation of your peers. Pure and simple." (Interview for Discover Magazine)

Thomas Kuhn (1922-1996, philosopher):
"Only when they must choose between competing theories do scientists behave like philosophers." (1970, Logic of Discovery or Psychology of Research)

Erving Goffman (1922-1982, sociologist):
"So I ask that these papers be taken for what they merely are: exercises, trials, tryouts, a means of displaying possibilities, not establishing fact." (Wikiquote)

Clifford Geertz (1926-2006, anthropologist):
"To look at the symbolic dimensions of social action — art, religion, ideology, science, law, morality, common sense — is not to turn away from the existential dilemmas of life for some empyrean realm of de-emotionalized forms; it is to plunge into the midst of them." (1973, The Interpretations of Cultures)

Noam Chomsky (1928-now, linguist):
"Science talks about very simple things, and asks hard questions about them. As soon as things become too complex, science can't deal with them... But it's a complicated matter: Science studies what's at the edge of understanding, and what's at the edge of understanding is usually fairly simple. And it rarely reaches human affairs. Human affairs are way too complicated. In fact even understanding insects is an extremely complicated problem in the sciences. So the actual sciences tell us virtually nothing about human affairs." (2011, Science in the Dock)

Peter Berger (1929-now, sociologist):
"The symbolic universe also orders history. It locates all collective events in a cohesive unity that includes past, present and future." (1966, The Social Construction Reality)

E. O. Wilson (1929-now, biologist):
"We are drowning in information, while starving for wisdom. The world henceforth will be run by synthesizers, people able to put together the right information at the right time, think critically about it, and make important choices wisely." (1998, Consilience: The Unity of Knowledge)

Carl Sagan (1934-1996, astronomer):
"We live in a society absolutely dependent on science and technology and yet have cleverly arranged things so that almost no one understands science and technology. That's a clear prescription for disaster." (1994, Bringing Science Down to Earth)

Stephen Jay Gould (1941-2002, biologist):

"Organisms are not billiard balls, propelled by simple and measurable external forces to predictable new positions on life's pool table." (119850, The Panda's Thumb)

Richard Leakey (1944-now, anthropologist):
"A vital leap in the evolution of intellectual capacity would have been the ability to form concepts, to conceive of individual objects as belonging to distinct classes, and thus do away with the almost intolerable burden of relating one experience to another. Concepts, moreover, can be manipulated and this is the root of abstract thought and of invention. The formation of concepts is also a necessary, but apparently not sufficient, condition for the emergence of language." (1977, Origins)

Simon Schama (1945-now, historian):
"Historians are left forever chasing shadows, painfully aware of their inability ever to reconstruct a dead world in its completeness however thorough or revealing their documentation." (1991, Dead Certainties)

Michio Kaku (1947-now, physicist):
"Mathematics... is the set of all possible self-consistent structures, and there are vastly more logical structures than physical principles." (1995, Hyperspace)

Bruno Latour (1947-now, philosopher):
"If one looks at the works of Newton to Einstein, they were never scientists in the way modernity understands the term." (Brainy Quote)

Stephen Hawking (1949-now, physicist):
"Even if there is only one possible unified theory, it is just a set of rules and equations. What is it that breathes fire into the equations and makes a universe for them to describe? The usual approach of science of constructing a mathematical model cannot answer the questions of why there should be a universe for the model to describe. Why does the universe go to all the bother of existing?" (1988, A Brief History of Time)

Iris Chang (1968-2004, historian):
"I have certainly amassed many historical research gathering skills." (Brainy Quote)