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In our earlier extracts from the writings of Kant, and even more in Hegel, we can see the style and language of philosophy becoming increasingly technical, with a consequent loss of the transparency and directness at which many of its earlier practitioners had aimed. In our own time, the writings of Hegel and his followers, in particular, have often been accused of being at best hard to follow, and at worst verging on the rankly unintelligible. At the start of the twentieth century, with the rise of the so-called ‘analytic’ movement, there was something of a revulsion against philosophical obscurantism, and a move towards a more down-to-earth approach. As far as the philosophy of knowledge is concerned, one important influence was the work of George Edward Moore, widely regarded as one of the founders of the analytical philosophy which now predominates in the English-speaking world.

In his famous essay ‘A Defence of Common Sense’ (1925), Moore pours a cold douche on the tortuous agonizings of many past philosophers about the possibility of genuine knowledge. He lists a number of basic ‘truisms’ of which he insists he is entitled to be quite certain – for example the proposition that the earth exists, and existed for a large number of years before he was born. (Remember that Descartes, in the Meditations (extract 4, above), had used his method of doubt – the dreaming argument, the hypothesis of a malicious deceiver – to call into question just such apparently obvious beliefs as the belief in an external world.) For Moore, such plain common-sense beliefs are just known to be true, and any philosopher who maintains the contrary is sooner or later bound to be trapped in inconsistency.

We can see here something of an echo of Hume’s scathing attacks against the wilder kinds of philosophical scepticism. But whereas Hume (extract 7, above) had pointed to our irresistibly strong human beliefs as being too strong for the sceptic to subvert, Moore suggests that what is wrong with philosophical scepticism is that it is inevitably trapped in a self-refuting paradox. The very fact that some philosophers have called into question the existence of the earth, for example, shows that the existence of the earth cannot be denied ‘for when I speak of “philosophers” I mean, of course, as we all do, exclusively philosophers who have been human beings, with human bodies that have lived on the earth’.

The argument is not entirely convincing as it stands, since there is surely nothing to prevent the sceptic presenting his or her position in a more guarded way that avoids commitment to the supposed common-sense view (Descartes, indeed, aimed to do just that). Moore none the less succeeds in raising the interesting thought that the philosopher’s job might be not so much to propound high-flown theories as to remove the confusions and mistakes of previous theorists. The idea was taken up in a more sophisticated way by the famous Austrian philosopher Ludwig Wittgenstein, who argued in On Certainty (first published in 1969, eighteen years after his death) that the basic propositions instanced by Moore form part of a fundamental framework that is unavoidable if it is even to make sense to raise questions about what we know: ‘I did not get my picture of the world by satisfying myself of its correctness. No: it is the inherited background against which I distinguish between true and false … All testing, all confirmation and disconfirmation of a hypothesis, takes place within a system. And this system is not a more or less arbitrary and doubtful point of departure for all our arguments; no, it belongs to the essence of what we call an argument. The system is not so much the point of departure as the element within which arguments have their life … I should like to say Moore does not know what he asserts he knows, but it stands fast for him, as also for me; regarding it as absolutely solid is part of our method of doubt and enquiry.’¹ Whatever judgement one passes on Moore’s approach, it continues to provoke important questions about the relationship between philosophical theorizing about knowledge and the seemingly unshakeable everyday beliefs which we all share.

In what follows I have merely tried to state, one by one, some of the most important points in which my philosophical position differs from positions which have been taken up by some other philosophers … I am going to begin by enunciating, under the heading (1), a whole long list of propositions, which may seem, at first sight, such obvious truisms as not to be worth stating: they are, in fact, a set of propositions, every one of which (in my own opinion) I know, with certainty, to be true …

(1) The propositions to be included in this list are the following. There exists at present a living human body, which is my body. This body was born at a certain time in the past, and has existed continuously ever since, though not without undergoing changes; it was, for instance, much smaller when it was born, and for some time afterwards, than it is now. Ever since it was born, it has been either in contact with or not far from the surface of the earth; and, at every moment since it was born, there have also existed many other things, having shape and size in three dimensions (in the same familiar sense in which it has), from which it has been at various distances (in the familiar sense in which it is now at a distance both from that mantelpiece and from that bookcase, and at a greater distance from the bookcase than it is from the mantelpiece); also there have (very often, at all events) existed some other things of this kind with which it was in contact (in the familiar sense in which it is now in contact with the pen I am holding in my right hand and with some of the clothes I am wearing). Among the things which have, in this sense, formed part of its environment (i.e., have been either in contact with it, or at some distance from it, however great) there have, at every moment since its birth, been large numbers of other living human bodies, each of which has like it, (a) at some time been born, (b) continued to exist from some time after birth, (c) been, at every moment of its life after birth, either in contact with or not far from the surface of the earth; and many of these bodies have already died and ceased to exist. But the earth had existed also for many years before my body was born; and for many of these years, also, large numbers of human bodies had, at every moment, been alive upon it; and many of these bodies had died and ceased to exist before it was born. Finally (to come to a different class of propositions), I am a human being, and I have, at different times since my body was born, had many different experiences, of each of many different kinds: e.g., I have often perceived both my own body and other things which formed part of its environment, including other human bodies; I have not only perceived things of this kind, but have also observed facts about them, such as, for instance, the fact, which I am now observing, that that mantelpiece is at present nearer to my body than that bookcase; I have been aware of other facts, which I was not at the time observing, such as, for instance, the fact, of which I am now aware, that my body existed yesterday and was then also for some time nearer to that mantelpiece than to that bookcase; I have had expectations with regard to the future, and many beliefs of other kinds, both true and false; I have thought of imaginary things and persons and incidents, in the reality of which I did not believe; I have had dreams; and I have had feelings of many different kinds. And, just as my body has been the body of a human being, namely myself, who has, during his lifetime, had many experiences of each of these (and other) different kinds; so, in the case of very many of the other human bodies which have lived upon the earth, each has been the body of a different human being, who has, during the lifetime of that body, had many different experiences of each of these (and other) different kinds.

(2) I now come to [a] single truism which, as will be seen, could not be stated except by reference to the whole list of truisms, just given in (1). This truism also (in my own opinion) I know, with certainty, to be true; and it is as follows: … Each of us (meaning by ‘us’, very many human beings of the class defined) has frequently known, with regard to himself or his body and the time at which he knew it, everything which, in writing down my list of propositions in (1), I was claiming to know about myself or my body and the time at which I wrote that proposition down … Just as I knew (when I wrote it down) ‘There exists at present a living human body which is my body’, so each of us has frequently known with regard to himself at some other time the different but corresponding proposition, which he could then have properly expressed by, ‘There exists at present a human body which is my body’; … and so on, in the case of each of the propositions enumerated in (1) …

In what I have just said, I have assumed that there is some meaning which is the ordinary or popular meaning of such expressions as ‘The earth has existed for many years past’. And this, I am afraid, is an assumption which some philosophers are capable of disputing. They seem to think that the question ‘Do you believe that the earth has existed for many years past?’ is not a plain question, such as should be met either by a plain ‘Yes’ or ‘No’, or by a plain ‘I can’t make up my mind’, but is the sort of question which can be properly met by: ‘It all depends on what you mean by ‘“the earth”’ and ‘“exists”’ and ‘“years”’… It seems to me that such a view is as profoundly mistaken as any view can be. Such an expression as ‘The earth has existed for many years past’ is the very type of an unambiguous expression, the meaning of which we all understand. Anyone who takes a contrary view must, I suppose, be confusing the question whether we understand its meaning (which we all certainly do) with the entirely different question whether we know what it means, in the sense that we are able to give a correct analysis of its meaning. The question what is the correct analysis of the proposition meant on any occasion … by ‘The earth has existed for many years past’ is, it seems to me, a profoundly difficult question, and one to which, as I shall presently urge, no one knows the answer. But to hold that we do not know what, in certain respects, is the analysis of what we understand by such an expression, is an entirely different thing from holding that we do not understand the expression. It is obvious that we cannot even raise the question how what we do understand by it is to be analysed, unless we do understand it. So soon, therefore, as we know that a person who uses such an expression is using it in its ordinary sense, we understand his meaning. So that in explaining that I was using the expressions used in (1) in their ordinary sense (those of them which have an ordinary sense, which is not the case with quite all of them), I have done all that is required to make my meaning clear.

But now, assuming that the expressions which I have used to express (2) are understood, I think, as I have said, that many philosophers have really held views incompatible with (2). And the philosophers who have done so may, I think, be divided into two main groups [A and B respectively] …

A… . Some philosophers, belonging to this group, have held that no propositions belonging to any of the classes in (2) are wholly true, while others have only held this with regard to some of the classes in (2) … All such views, whether incompatible with all of the propositions in (1), or only with some of them, seem to me to be quite certainly false; and I think the following points are specially deserving of notice with regard to them.

(a) If any of the classes of propositions in (2) is such that no proposition of that class is true, then no philosopher has ever existed, and therefore none can ever have held with regard to any such class, that no proposition belonging to it is true. In other words, the proposition that some propositions belonging to each of these classes are true is a proposition which has the peculiarity, that, if any philosopher has ever denied it, it follows from the fact that he has denied it, that he must have been wrong in denying it. For when I speak of ‘philosophers’ I mean, of course (as we all do), exclusively philosophers who have been human beings, with human bodies that have lived upon the earth, and who have at different times had many different experiences. If, therefore, there have been any philosophers, there have been human beings of this class; and if there have been human beings of this class, all the rest of what is asserted in (1) is certainly true too. Any view, therefore, incompatible with the proposition that many propositions corresponding to each of the propositions in (1) are true, can only be true, on the hypothesis that no philosopher has ever held any such view. It follows, therefore, that, in considering whether this proposition is true, I cannot consistently regard the fact that many philosophers, whom I respect, have, to the best of my belief, held views incompatible with it, as having any weight at all against it. Since, if I know that they have held such views, I am, ipso facto, knowing that they were mistaken; and, if I have no reason to believe that the proposition in question is true, I have still less reason to believe that they have held views incompatible with it; since I am more certain that they have existed and held some views, i.e., that the proposition in question is true, than that they have held any views incompatible with it.

(b) It is, of course, the case that all philosophers who have held such views have repeatedly, even in their philosophical works, expressed other views inconsistent with them: i.e., no philosopher has ever been able to hold such views consistently. One way in which they have betrayed this inconsistency, is by alluding to the existence of other philosophers. Another way is by alluding to the existence of the human race, and in particular by using ‘we’ in the sense in which I have already constantly used it, in which any philosopher who asserts that ‘we’ do so and so, e.g., that ‘we sometimes believe propositions that are not true’, is asserting not only that he himself has done the thing in question, but that very many other human beings, who have had bodies and lived upon the earth, have done the same. The fact is, of course, that all philosophers have belonged to the class of human beings which exists only if (2) be true: that is to say, to the class of human beings who have frequently known propositions corresponding to each of the propositions in (1). In holding views incompatible with the proposition that propositions of all these classes are true, they have, therefore, been holding views inconsistent with propositions which they themselves knew to be true; and it was, therefore, only to be expected that they should sometimes betray their knowledge of such propositions. The strange thing is that philosophers should have been able to hold sincerely, as part of their philosophical creed, propositions inconsistent with what they themselves knew to be true; and yet, so far as I can make out, this has really frequently happened …

B. This view, which is usually considered a much more modest view than A, has, I think, the defect that, unlike A, it really is self-contradictory, i.e., entails both of two mutually incompatible propositions. Most philosophers who have held this view, have held, I think, that though each of us knows propositions corresponding to some of the propositions in (1), namely to those which merely assert that I myself have had in the past experiences of certain kinds at many different times, yet none of us knows for certain any propositions either of the type which assert the existence of material things or of the type which assert the existence of other selves, beside myself, and that they also have had experiences. They admit that we do in fact believe propositions of both these types, and that they may be true: some would even say that we know them to be highly probable; but they deny that we ever know them, for certain, to be true. Some of them have spoken of such beliefs as ‘beliefs of Common Sense’, expressing thereby their conviction that beliefs of this kind are very commonly entertained by mankind: but they are convinced that these things are, in all cases, only believed, not known for certain; and some have expressed this by saying that they are matters of Faith, not of Knowledge.

Now the remarkable thing which those who take this view have not, I think, in general duly appreciated, is that, in each case, the philosopher who takes it is making an assertion about ‘us’ – that is to say, not merely about himself, but about many other human beings as well. When he says ‘No human being has ever known of the existence of other human beings’, he is saying: ‘There have been many other human beings beside myself, and none of them (including myself) has ever known the existence of other human beings’. If he says: ‘These beliefs are beliefs of Common Sense, but they are not matters of knowledge’, he is saying: ‘There have been many other human beings, beside myself, who have shared these beliefs, but neither I nor any of the rest have ever known them to be true’. In other words, he asserts with confidence that these beliefs are beliefs of Common Sense, and seems often to fail to notice that, if they are, they must be true; since the proposition that they are beliefs of Common Sense … logically entails the proposition that many human beings, beside the philosopher himself, have had human bodies, which lived upon the earth, and have had various experiences, including beliefs of this kind. This is why this position, as contrasted with positions of group A, seems to me to be self-contradictory. Its difference from A consists in the fact that it is making a proposition about human knowledge in general, and therefore is actually asserting the existence of many human beings, whereas philosophers of group A in stating their position are not doing this: they are only contradicting other things which they hold. It is true that a philosopher who says ‘There have existed many human beings beside myself, and none of us has ever known the existence of any human beings beside himself’, is only contradicting himself if what he holds is ‘There have certainly existed many human beings beside myself’ or, in other words, ‘I know that there have existed other human beings beside myself’. But this, it seems to me, is what such philosophers have in fact been generally doing. They seem to me constantly to betray the fact that they regard the proposition that those beliefs are beliefs of Common Sense, or the proposition that they themselves are not the only members of the human race, as not merely true, but certainly true; and certainly true it cannot be, unless one member, at least, of the human race, namely themselves, has known the very things which that member is declaring that no human being has ever known.

Nevertheless, my position that I know, with certainty, to be true all of the propositions in (1), is certainly not a position, the denial of which entails both of two incompatible propositions. If I do know all these propositions to be true, then, I think, it is quite certain that other human beings also have known corresponding propositions: that is to say (2) also is true, and I know it to be true. But do I really know all the propositions in (1) to be true? Isn’t it possible that I merely believe them? Or know them to be highly probable? In answer to this question, I think I have nothing better to say than that it seems to me that I do know them, with certainty. It is, indeed, obvious that, in the case of most of them, I do not know them directly: that is to say, I only know them because, in the past, I have known to be true other propositions which were evidence for them. If, for instance, I do know that the earth had existed for many years before I was born, I certainly only know this because I have known other things in the past which were evidence for it. And I certainly do not know exactly what the evidence was. Yet all this seems to me to be no good reason for doubting that I do know it. We are all, I think, in this strange position that we do know many things, with regard to which we know further that we must have had evidence for them, and yet we do not know how we know them, i.e., we do not know what the evidence was. If there is any ‘we’, and if we know that there is, this must be so: for that there is a ‘we’, is one of the things in question. And that I do know that there is a ‘we’, that is to say, that many other human beings, with human bodies, have lived upon the earth, it seems to me that I do know, for certain.

If this first point in my philosophical position, namely my belief in (2), is to be given any name, which has actually been used by philosophers in classifying the positions of other philosophers, it would have, I think, to be expressed by saying that I am one of those philosophers who have held that the ‘Common Sense view of the world’ is, in certain fundamental features, wholly true. But it must be remembered that, according to me, all philosophers, without exception, have agreed with me in holding this: and that the real difference, which is commonly expressed in this way, is only a difference between those philosophers, who have also held views inconsistent with these features in ‘the Common Sense view of the world’, and those who have not.

The features in question (namely, propositions of any of the classes defined in defining (2)) are all of them features, which have this peculiar property – namely, that if we know that they are features in the ‘Common Sense view of the world’, it follows that they are true: it is self-contradictory to maintain that we know them to be features in the Common Sense view, and that yet they are not true; since to say that we know this, is to say that they are true. And many of them also have the further peculiar property that, if they are features in the Common Sense view of the world (whether we know this or not), it follows that they are true, since to say that there is a ‘Common Sense view of the world’ is to say that they are true. The phrases ‘Common Sense view of the world’ or ‘Common Sense beliefs’ (as used by philosophers) are, of course, extraordinarily vague; and, for all I know, there may be many propositions which may be properly called features in ‘the Common Sense view of the world’ or ‘Common Sense beliefs’, which are not true, and which deserve to be mentioned with the contempt with which some philosophers speak of ‘Common Sense beliefs’. But to speak with contempt of those ‘Common Sense beliefs’ which I have mentioned is quite certainly the height of absurdity. And there are, of course, enormous numbers of other features in the Common Sense view of the world which, if these are true, are quite certainly true too: e.g., that there have lived upon the surface of the earth not only human beings, but also many different species of plants and animals, etc., etc.