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Wittgenstein & Occam: A Philosophical Conversation

Christian Erbacher and Lu Jiang imagine a meeting between a modern and a medieval philosopher.

Although William of Occam (1285-1349) is one of the very few authors explicitly mentioned in Ludwig Wittgenstein’s Tractatus Logico-Philosophicus (1921), the relation of Wittgenstein’s and Occam’s philosophy has not been extensively investigated. This article brings the two thinkers into a dialogue in which they mutually illuminate their views on the logical analysis of ordinary language, taking into account their conception, fundamental to both philosophers, of logic as an activity. The dialogue is taken with very few alterations from Occam’s Summa Logicae and Wittgenstein’s Tractatus Logico-Philosophicus.

Wittgenstein and Occam 1


Wittgenstein enlisted in the Austrian army at the beginning of August 1914, only ten days after the outbreak of World War I. By that time the young philosopher’s basic views on language and logic were largely settled. Wittgenstein had hoped to finish his book despite the war, but he experienced a serious crisis that made work impossible.

In the middle of his depression, around the turn of the year 1914/15, Wittgenstein was appointed adjutant to an Austrian lieutenant called Gürth, and shortly afterwards was sent with him to Vienna. Early in1915, Wittgenstein and Gürth visited Klosterneuburg monastery in the vicinity of Vienna. Here the following encounter took place, leaving Wittgenstein freshly inspired to finish his book.

Taking a break from chatting with Gürth, Wittgenstein goes for a stroll around the monastery cloister. He observes a monk, about fifty years old, leaving the library and entering the cloister. The monk is wearing a brown cowl and is carrying a leatherbound volume of Guillelm von Moerbeke’s translation of Aristotle’s Metaphysics. He is murmuring something. The murmur attracts Wittgenstein’s attention.

Monk: Entia non sunt multiplicanda praeter necessitatem

Wittgenstein: Was sagen Sie da?

(The monk looks up.)

Monk: Entschuldige, versteh nicht, bin Engelisch, Anglicus sum.

Wittgenstein: Oh, you don’t speak German. Never mind, I do speak English – although I am never quite sure about the spelling. What was that you just said?

Monk: ‘Entities shouldn’t be multiplied without necessity’.

Wittgenstein: What makes you say that?

Monk: (The monk points to the book in his hand.) This new translation of the nouns in Aristotle’s Metaphysicsmakes scholars believe that the Greek philosophers were talking about certain entities that they thought really existed. But philosophers should only introduce entities if there is no other way to explain a problem than by doing so.

Wittgenstein: You’re talking about ‘Occam’s Razor’, aren’t you?

Monk: Occam’s razor?

Wittgenstein: William of Occam, an important scholastic philosopher. You must know him! He is best known for the maxim you quoted. It might be fruitful for logical analysis.

Monk: Well, I use this principle often, indeed. But it is not my razor. Rather, it seems to me a commonplace in logic. Even Duns Scotus, my Brother, mentioned it. Didn’t you know that? I have to argue against his realist position again and again and again. For example in my Summa Logicae, I write…

Wittgenstein: Wait a moment. Do you mean you are Occam?

Monk: Yes, of course. Why are you so astonished about that? I am William, and ‘Occam’ – or ‘Ockham’ – is the village I was born in. And who is this young man I have the pleasure to meet?

Wittgenstein: Eh, Wittgenstein, Ludwig. I was born in Vienna. (To himself) Am I mad?

Occam: Nice to meet you, Ludwig of Vienna. Shall we walk round this garden together for a while?

Wittgenstein: Sorry? Yes, why not?

(They begin to walk side by side in the cloister.)

Wittgenstein and Occam 2

Wittgenstein: I think the point of your maxim is that if a sign is useless, it is meaningless, isn’t it?

Occam: Well, I use this principle to slim down the overpopulated metaphysical realm of Duns Scotus. But my favourite expression of it is frustra fit per plura quod potest fieri per pauciora. I suppose you know a little Latin? One might translate it as: ‘It is superfluous to do with more what you can do with less’. But the formulation I mentioned before is the more common one.

(A pause.)

Occam: You know, many of the moderni – as I call the Realists – introduce a lot of suspicious entities into their theories. They do this through creating new terms for abstract categories, such as ‘humanitas’ or ‘animalitas’: ‘humanity’ or ‘animal’. And then they say that behind those terms one should also assume corresponding entities! But not every word has a corresponding object outside our minds.

Wittgenstein: I couldn’t agree more. And you know, all philosophical problems emerge from similar mistakes. I believe they result from the mistaken way one formulates the problems; and the method of formulating them often rests on a misunderstanding of the logic of language. That is why philosophers should only clarify the logic of language – because this helps to clarify the propositions that lead to the metaphysical problems. These problems disappear once the logic of their formulation is clarified.

Occam: Well, young Wittgenstein, you sound radical. But remember that temperance is a virtue. My main concern, however, is that the apparently substantive form of these newly invented category terms in philosophy must not mislead us into believing that they stand for things, as the Realists do. But you already seem to be very sensitive to the tendencies of our language to mislead thought. Tell me more.

Wittgenstein: It is of the greatest importance to clarify propositional signs. Look: man possesses the capacity to construct languages in which every sense can be expressed. But language often disguises the thought! From the external form of the clothes one cannot infer the shape of the body they cover. This is not the purpose for which clothes are usually made. It is like this with language. I’ll give you an example. In the language of everyday life it very often happens that the same word signifies in two different ways – and therefore in fact belongs to two different symbols. Take the proposition ‘Green is green’, meaning the man Green is green with envy, or some such thing. Here the first word is a proper name, and the last an adjective. These words don’t merely have different meanings, they are different symbols.

Occam: This is true. You might say that the grammar does not transparently represent the logical structure of the language. This reminds me of the vast literature of the so-called ‘insolubilia’ or ‘sophismata’ that bloomed during the Twelfth Century. The sophismata are paradoxes – like the liar paradox – or contradictions which result from the confusion of the grammatical with the logical structure. Do you know the Donkey Sophisma? I will write it in both Latin and English for you.

(They stop. Occam takes a piece of chalk out of his pocket and writes on the ground:)

Episcopi sunt asini. These donkeys are the Bishop’s.
Episcopi canent missam. Bishops sing mass.
Asini canent missam. Therefore: Donkeys sing mass.

Occam: You see, this sophisma has the structure of a logical syllogism in Latin, but it only works through a grammatical confusion: the ‘episcopi’ in the first premise is genitive, whereas the ‘episcopi’ in the second premise is nominative. This confusion comes into being by taking the syllogism merely according to its surface appearance, and the conclusion is nonsense. The English translation shows already that the syllogism doesn’t logically conclude. Linguistic appearance can mislead thought.

Wittgenstein: It is so, William.

Occam: Authors of the Twelfth Century detected this problem: through this and many other sophismata we discovered that the apparent structure of what is being said is not identical with its logical structure. So we have realized that the valid figures and modes of Aristotelian syllogisms cannot be automatically applied through our daily language. Therefore, as the Donkey Sophisma shows, one of the main concerns of the logicians should be to disambiguate sentences articulated in the daily language before they are to be used as premises in any guaranteed valid logical syllogism.

Wittgenstein: You are right. I believe that the whole of philosophy is full of such confusions. Most propositions and questions that have been written about philosophical matters are in this way not false, but senseless. They are of the same kind as the question ‘Is the Good more or less identical to the Beautiful?’ And so it is not surprising that the deepest problems are really no problems at all.

Occam: Do not move too fast, young Wittgenstein. There are ways to deal with this problem of language. In fact, in my Summa, I do strive to work out the rules for a logically correct use of language. My analysis aims to clarify the ambiguity in sentences and to dispel the illusions which are created by apparent linguistic structure.

Wittgenstein: A perfect symbolism is necessary to avoid these errors – a symbolism, that is to say, which obeys the logical grammar – the logical syntax. That is what I intend to develop – a notation that shows the logical structure of sentences.

Occam: Consider that you may serve your purpose just as well by making restrictions that constrain a logically correct use of ordinary language. You can find plenty of such restrictions in my Summa Logicae, the whole aim of which is to teach students the rules of logic and their right application. I strive to improve the structure of language and to set up norms for its logical use. For example, in the fourth section of the third part, I treat a wide range of fallacies which result from the ambiguity of ordinary language. There are altogether thirteen different kinds of fallacies in the book, and the first three concern linguistic ambiguity. One of them, the fallacy of equivocation, is the mention of many things by using the same word – the same sign – just as you suggested.

Wittgenstein: The word ‘is’ is another highly ambiguous example. It can appear as a copula – linking a thing to its properties – or it can be the sign of the equality of two things, or it can be an expression of existence. This is the mess with ordinary language! No wonder that philosophical problems emerge.

Occam: How interesting to hear you mention the word ‘is’. Logicians use to elaborate upon it, for instance in the Treatise on Syncategoremata of William of Sherwood – who was a countryman of mine, by the way. He distinguished two different ways in which the verb ‘is’ can indicate existence. In the first, ‘is’ indicates actual existence, and in the second, habitual existence. It’s the essence and the accidents of a thing, as some might say – except that Sherwood didn’t share the opinion of some of his contemporaries that the verb ‘is’ has the function of combining the thing and its properties. Sherwood’s view was not uncommon, although later scholastics such as Thomas Aquinas still held the view that ‘is’ indicates different ways of being – the so-called modi essendi. It was not until Duns Scotus that the two functions of ‘is’ – as an indicator for existence and as the sign for combination – were eventually recognized. I follow Duns Scotus in this respect, and make use of this distinction several times both in my philosophical and in my theological works. We do agree on many philosophical questions, actually. Our strongest disagreements are methodological. That’s why I use my parsimony principle to criticize him.

Wittgenstein: Aha.

Wittgenstein and Occam 3

Occam: Moreover, the theory of neutral propositions can only be properly understood by understanding the copula ‘is’. Used this way it combines the subject and predicate terms into a ‘complexum’ – a sentence: ‘The rose is red’, for instance. But the copula ‘is’ does not have the function of asserting, as used to be thought by older scholastics.

Wittgenstein: Wait, this sounds familiar. I think you are separating the sense of a proposition from its truth value. This is just what I do. Every proposition must already have a sense, and asserting it as true cannot give it a sense, for what is being asserted is the sense of the proposition. The same holds of denial. Now, if one does not observe that propositions already have a sense independent of the facts, one can easily believe that ‘true’ and ‘false’ are relations between signs and things signified. I thought that nobody would understand if I say this!

Occam: (Scratching his head) Sorry?

Wittgenstein: An illustration to explain the concept of truth, then: Imagine a black blot on white paper. The form of the blot can be described by saying of each point of the paper whether it is white or black. But to be able to say that a point is black or white, I must first know under what conditions a point is called white or black. Similarily, in order to be able to say that a sentence is true, I must have determined under which conditions I call this sentence true. By determining these conditions I determine the sense of the proposition. That’s it. To understand a proposition means to know what is the case if it is true.

Occam: I am beginning to see what you mean. Go on.

Wittgenstein: My idea is that propositions can be true or false only by being pictures of reality, so that instead of saying, ‘This proposition has such-and-such a sense’, one can say, ‘This proposition represents such-and-such a state of affairs’. Thus to have meaning, the configuration of names in the propositional sign – in the sentence, as you might call it – must possibly correspond to the configuration of the objects in the actual state of affairs. One name stands for one thing, and another for another thing, and they are connected together in such-and-such a way, as represented in the propositional sign. And so the whole, like a living picture, presents the fact. So you see, the possibility of meaningful propositions is based upon the principle of the representation of objects by signs. The name represents the object.

Occam: If I understand you correctly, you are talking about something comparable with what I call the ‘suppositio personalis’.

Wittgenstein: Possibly.

Occam: Let me explain. My logic contains two sorts of signs – categorical and syncategorical. Only the categorical ones have significations – meaning that they stand for something other than themselves. That might be what you call ‘representation’. In a sentence, these categorical terms have a supposition. Supposition in its strict understanding, is a sort of taking the place of another thing. Thus, when we use the term for a thing, and the term is truly predicated of that thing, the term ‘supposits’ for that thing. Actually, I distinguish between three different kinds of supposition: the material, the simple, and the personal supposition. It is important that only in the personal supposition does a term stand for a thing in the extra-mental world – you called the personal supposition a ‘name’. And a categorical term, which can stand for an object in reality, can have supposition only in a sentence – or what you called a ‘proposition’.

Wittgenstein: This sounds like what I learned from Frege: only propositions have sense; only in the context of a proposition has a name meaning; a proposition can be an incomplete picture of a certain state of affairs, but it is always itself a complete picture.

Occam: Now let us go further. Listen, young Ludwig. There are not only categorical terms, there are also syncategorical terms. They are most important for logic, and they do not represent. They are only signs with which we do logical operations. They can’t be the subject or predicate term of the sentence; they are formal parts of complex sentences instead. Let me explain it this way: the categorical sentence is the simplest form among all sentences. It is the building brick of all more complex sentences. It is made up of the subject term, the copula ‘is’ and the predicate term: ‘The tree is green’, for instance. But any sentence with a syncategorical sign is already a complex one. For example, the sentence ‘All human beings are mammals’ is not a simple sentence because of the quantifier ‘All’. Or in the sentence ‘Only Socrates is wise’, the word ‘only’ is a syncategorical term. This sentence, although it looks simple, is logically equivalent to the complex sentence ‘Socrates is wise, and nothing other than Socrates is wise’.

Wittgenstein: I think a lot about propositional building bricks. I call them ‘elementary propositions’. I believe that every complex proposition is a composition of elementary propositions. And they are combined, as you say, by logical operations.

Occam: Let me make my point really clear: the so-called syncategorical terms are signs for logical operations, and they don’t have any signification themselves. Do you agree?

Wittgenstein: That’s my fundamental thought! Denial, logical addition, logical multiplication, and so on, are logical operations. They show how we can proceed from one form of proposition to another, but they do not themselves represent. That means that there are no such things as logical objects or logical constants.

Occam: You are right – the signs of logical operations belong to the second intentions, which are products of our mental activities, and are not themselves things. People sometimes mistake the mental concepts for the entities to which the signs in the written or spoken language refer. But although I mention the word ‘mental’, I am not postulating the existence of mental entities. We should recall that mental activities aren’t mental entities. It is true that the individual mind is the subject of mental activities, and thus the activities exist somehow. In my Commentary on Peter Lombard’s Sententiarum, I made several suggestions for the nature of mental concepts, which in the Aristotelian tradition are taken to be passions of the soul. I myself favour the explanation that concepts are activities of the mind. I consider this investigation into the nature of concepts to be a topic of metaphysics, which leaves it open which explanation of them is more proper, because it can neither be shown through experience nor demonstrated by logical reasoning. But what type of existence these activities have is not crucial for my inquiry into the nature of logic. Logically speaking, concepts are like their counterparts in the spoken and written language: nothing mysterious, but only signs with which we conduct logical thinking. We can, if you want, cut these logical objects with my ‘razor’.

Wittgenstein: Let’s do it!

Occam: Well, let’s agree that logic is not about real entities, as natural philosophy is. Let’s also agree that logic is not a speculative science, it is a practical science.

Wittgenstein: I do agree. The goal of philosophy is the logical clarification of thoughts. The result of philosophy is not a number of philosophical propositions, but to make propositions clear. Philosophy is not a theory, but an activity.

Occam: How true!

(At this point, Lieutenant Gürth enters the cloister. He’s looking for Wittgenstein.)

Occam: (In a low voice) Look, we’ve had a pleasant conversation. We have gone one long circle in this garden. Let that be good for today, before we start to disagree. I have a feeling that we should take up the discussion again some time, and see where we differ. For now, I have to leave.

(Occam disappears.)

Gürth: Ludwig, Ludwig, mach ka Schmäh, und kom ins Beisl. [English translation from Gürth’s Viennese dialect: “Ludwig, Ludwig, don’t mess around, and come to the pub.”]


After this encounter Wittgenstein began to work again. A diary entry from that time reads: “It was that, what I want to call my strong scholastic feeling, which was the cause of my best discoveries.” Entries over subsequent weeks indicate increasing creativity: “I work” – “I work again!” – the “mercy of work!”

© Christian Erbacher & Lu Jiang 2015

Christian Erbacher is a postdoc-researcher, at the Wittgenstein Archives at the University of Bergen, Norway, and at the University of Siegen, Germany. He is currently researching in order to write the intellectual history of editing Wittgenstein.

Lu Jiang is Lecturer for Philosophy at the Sun Yat-sen University, Guangzhou, China. Her special research fields are, among others, Medieval Philosophy, Renaissance Logic, and Aristotle.

• This work was funded by Deutscher Akademischer Auslandsdienst (DAAD) and Norges Forskningsråd (NFR) in connection with the German-Norwegian exchange project ‘Wittgenstein and Medieval Philosophy’. Revision of the text was supported by NFR in connection with the research project ‘Shaping a domain of knowledge by editorial processing: the case of Wittgenstein’s work’.

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