I am interested in B. Russell's quote:

Science is what we know; philosophy is what we don't know.

What is he saying here in terms of a definition of philosophy? In his sense, is that correct to say that philosophy cannot give us more knowledge except for better organizing and explaining our ignorance?

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    Welcome aboard - don't forget to upvote useful answers and comments as well as accept an answer that addresses your question adequately! :)
    – MmmHmm
    Oct 26, 2016 at 14:51

4 Answers 4


"A man might say, with enough truth to justify a joke: 'Science is what we know, and philosophy is what we don’t know.'"
-Bertrand Russell
Philosophy for Laymen
Universities Quarterly 1 (Nov 1946), 38-49
Unpopular Essays, Chapter 2 (George Allen & Unwin, 1951)

No, philosophy is not taxonomy. Philosophy is respect for obtaining knowledge - whether this be where there is ignorance and false arguments duly rejected, or, advancing hypotheses and the means by which to do so. As the term has translated from the Greek through the Latin, philosophy is "love of wisdom".

Note that the quote above is from his later years of writing and in particular from a chapter called, "Philosophy for Laymen". Consider the following quote from his introduction to The History Of Western Philosophy:

"Science tells us what we can know, but what we can know is little, and if we forget how much we cannot know we become insensitive to many things of very great importance. Theology, on the other hand, induces a dogmatic belief that we have knowledge where in fact we have ignorance, and by doing so generates a kind of impertinent insolence towards the universe. Uncertainty, in the presence of vivid hopes and fears, is painful, but must be endured if we wish to live without the support of comforting fairy tales. It is not good either to forget the questions that philosophy asks, or to persuade ourselves that we have found indubitable answers to them. To teach how to live without certainty, and yet without being paralyzed by hesitation, is perhaps the chief thing that philosophy, in our age, can still do for those who study it."

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    Noon means 'The Ninth Hour', Tragedy means 'the song of the wild goat', Nice comes from the Latin for ignorant, Pamphlet comes from a Latin phrase for a love poem and War comes from the Germanic root meaning to confuse. You can't base an view on what philosophy is simply on the origin of the word and expect that to be taken as truth.
    – user22791
    Jan 10, 2017 at 11:25
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    @Isaacson and yet it is etymological fact that philosophy is love of wisdom, i.e. respect for obtaining knowledge - and this translation has stood for 2500+ years. If you were alive in the 70s then you'll know that philosophy means never having to say you're sorry for obtaining empirical verification of what is.
    – MmmHmm
    Jan 10, 2017 at 11:30
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    I don't understand what you could mean by " it is etymological fact that philosophy is love of wisdom". Etymology is the study of the origins of words, it does not define them.
    – user22791
    Jan 10, 2017 at 12:15
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    @Isaacson Did I say "philosophy = love of wisdom" is a definition? It's not. It's simply translation of the original Greek, unchanged now for over 2500+years. Such meaning is simply empirical (etymological) fact. Of course there are many definitions; w/each dictionary a different one, but if a definition does not evidence "love of wisdom" then it is misnomer (e.g. using "philosophy" for opinions, beliefs or personal sentiment, "a way of looking at things") as philosophy requires knowledge. See Grice
    – MmmHmm
    Jan 10, 2017 at 17:53
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    You can't just substitute statements like "meaning is ... empirical (etymological) fact" for reasoned argument. As I have made abundantly clear in the examples I gave above, meaning is definitely not etymology, War is a violent confrontation between to states, not confusion, A pamphlet is a paper with a small amount of information on it, not a love poem. Noon is twelve o'clock, not nine. The meaning of words is what we use them for and those who make most use of the word philosophy (philosophers) do not now define it simply as "love of wisdom", regardless of it's original meaning.
    – user22791
    Jan 10, 2017 at 18:31

I think it quite likely that he's saying exactly that. Russell, pretty much from 1905 on and more so in later life, considered that knowledge derived from only two sources; facts about objects (derived from the scientific method) and certain facts about ourselves (really a special class of object, which, by direct acquaintance we already know and have no need to verify independently.

His philosophy centred around better describing these facts about ourselves, such as logic and ethics so that apparent false conclusions and conflicts would dissolve. In that sense, it was not his intention to give us more knowledge by philosophy, but to better describe the knowledge we have (and knowledge we cannot, or do not have).

In fact From Russell's view of the sources of knowledge, philosophy could not possibly advance new knowledge, he says of truths there are "...those which merely state what is given in sense, and also certain abstract logical and arithmetical principles, and (though with less certainty) some ethical propositions”.

In The impact of Science on Society he states that "...Science, ever since the time of the Arabs, has had two functions: (1) to enable us to know things..." and in My Philosophical Development "I still think that truth depends upon a relation to fact, and that facts in general are nonhuman"

I think the failure of Russell's work on the foundation of Mathematics made him much more skeptical even of the second type of intuitive knowledge, leading him to statements like the one you've found.

  • Russell had quite a sense of humor. The full quote is: "A man might say, with enough truth to justify a joke: 'Science is what we know, and philosophy is what we don’t know'."
    – MmmHmm
    Jan 10, 2017 at 21:31
  • @Mr.Kennedy The context of the quote is irrelevant, what I'm saying is that by his actions (such as the rejection of Kant's views on time because they clashed with Einstein's) Russell clearly indicated that he considered the results of scientific investigation to be both different and superior to those resulting from philosophical investigation. Whether we call these two results 'knowledge' and 'ignorance' does not matter, what matters is that they are of different sorts with the one superior to the other.
    – user22791
    Jan 11, 2017 at 10:07
  • Not quite. Again, you need to read (and the idea is to answer) the OP's question and not simply run amok with your own agenda, e.g. the OP asks "What is he saying here in terms of a definition of philosophy?" To answer that question, the entire sentence applies especially considering that Russell's remark is not in terms of a definition of philosophy. In any sense that one might interpret Russell so, "A man might say, with enough truth to justify a joke..." applies. Note that justifying jokes is not philosophy.
    – MmmHmm
    Jan 11, 2017 at 20:29

@Mr.Kennedy has made a good answer.

And @Issacson objection that

 etymology ≠ definition

is true in general. However I believe in this case

etymology+history = definition

is viable at least in approximation.

In Socrates time what we (today) call philosophers were called sophists. Socrates – very much a sophist by the standards of his day – did not like their...

  1. Overuse and over emphasis on rhetoric
  2. Money charging
  3. Making truth subservient to the utterer

So he suggested the element of love – philos – be conjoined to sophia – knowledge. The fact that Socrates could die for his convictions put the seal on his loving conviction. And the term stuck.

2500 years is a long time...

And most practitioners have not just not shown the passion of Socrates they've even forgotten that it was the distinguishing feature.

Ideally therefore, if we follow Socrates(Plato) not just in detail but in intent, philosophers should be called sophists and their profession sophistry when love is absent.


This is a general, and relatively common way of conceptualizing the difference between science and philosophy. Science deals with well-defined topics within already established structures, that is why it is about "what we know." Of course, we discover new results within science all the time, but we know what we are looking for, and we know what we expect (which is why we know when results depart from expectations).

Philosophers are comfortable much further out from shore on the conceptual ocean. Philosophical ideas don't have the structural support that scientific ideas have, they are about topics we haven't tamed yet, thus "what we don't know." For example, after all this time, we still don't really know why one person likes one piece of art, and another person hates it. We have plenty of theories, and we've noted some correlations, but the topic of aesthetics is still essentially philosophical and speculative. If we ever understand it to the point where we can confidently and consistently predict it, it will have become a science.

Thus, it's not the case that philosophy solely organizes ignorance, or that it is incapable of expanding knowledge, it's that it does not expand knowledge systematically, like science. Every scientist, however, was preceded by a philosopher.

  • I'm not sure I understand how you get from your second paragraph to your third, are they meant to be related? You seem to be saying in your second that philosopher's ideas about aesthetics are just speculation and if they ever become more conclusive they will become science, then jump to "Thus, it's not the case that philosophy ... is incapable of expanding knowledge". What knowledge is there is speculation about aesthetics? I agree with your conclusion, that philosophy can expand or at least reveal knowledge, but it would be only in the realm of logic or analytical philosophy, not aesthetics.
    – user22791
    Jan 10, 2017 at 16:24
  • Just a gentle reminder that Russel's and Wittgenstein's 'Tractatus' by their own estimation was a failed project. No doubt Russell was a brilliant person, but in the end not much of a thinker. He was better off sticking with the nuts and bolts of mathematics. He was also, by reputation, quite a crank and a 'mister-know-it-all.' So it is not difficult to dismiss whatever he said or meant in the above question. As Kant once explained, 'not all minds are built to contemplate first Philosophy'. Or something close to that. Charles M Saunders
    – user37981
    Apr 3, 2019 at 20:05

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