I figured I’d repost this since Christmas is coming up. The link to amazon is at the bottom. ; )

‘An Essay on Metaphysics’ by Robin George Collingwood

IV

ON PRESUPPOSING

Whenever anybody states a thought in words, there are a great many more thoughts in his mind than are expressed in his statement. Among these there are some which stand in a peculiar relation to the thought he has stated: they are not merely its context, they are its presuppositions.

I write these words sitting on the deck of a ship. I lift my eyes and see a piece of string—a line I must call it at sea—stretched more or less horizontally above me. I find myself thinking ‘that is a clothes-line’, meaning that it was put there to hang washing on. When I decide that it was put there for that purpose I am presupposing that it was put there for some purpose. Only if that presupposition is made does the question arise, what purpose? If that presupposition were not made, if for example I had thought the line came here by accident, that question would not have arisen, and the situation in which I think ‘that is a clothes-line’ would not have occurred.

The priority affirmed in the word presupposition is logical priority. It is not a priority in time, whether that time belong to the history of the clothesline or to the history of my thoughts about it. When I say that its being for some purpose is a presupposition of its being for that purpose, that it first had a kind of general or indeterminate purposiveness, and that then, when it was rigged as a clothes-line, it exchanged this general or indeterminate purposiveness for a particular or determinate one by beginning to serve the purpose of hanging up washing to dry. I am not now asking whether anything like this really happened or not when the line was put up; I am only referring to when I used the word ‘presupposition’

Nor did I mean that my thoughts about the clothesline moved from ‘that line is meant for something’ to ‘that line is meant to hang washing on’. They might have moved in that way, and if I had been thinking about the line in an orderly or scientific manner I should have seen to it that they did move in that way; but as a matter of fact they did not. The thought ‘that is a clothes-line’ came plump into my mind, so far as I am aware, all at once and unheralded. Only by a kind of analysis, when I reflect upon it, do I come to see that this was a presupposition I was making, however little I was aware of it at the time.

Here lies the difference between the desultory and casual thinking of our unscientific consciousness and the orderly and systematic thinking we call science. In unscientific thinking our thoughts are coagulated into knots and tangles; we fish up a thought out of our minds like an anchor foul of its own cable, hanging upside-down and draped in seaweed with shellfish sticking to it, and dump the whole thing on deck quite pleased with ourselves for having got it up at all. Thinking scientifically means disentangling all this mess, and reducing a knot of thoughts in which everything sticks together anyhow to a system or series of thoughts in which thinking the thoughts is at the same time thinking the connexions between them.

Logicians have paid a great deal of attention to some kinds of connexion between thoughts, but to other kinds not so much. The theory of presupposition they have tended to neglect; and this is perhaps why the theory of metaphysics, which depends on it, has been allowed to remain in an unsatisfactory condition. I will try to state so much of this theory as seems necessary for my present purpose. For the sake of reference later on, I will sate it in a formal manner, in numbered propositions, with definitions of such terms as are used in sense they do not bear in ordinary English usage, or of terms whose meaning in ordinary usage depends on the propositions I am expounding. In expounding these propositions I shall not be trying to convince the reader of anything, but only to remind him of what he already knows perfectly well.

Prop. 1. Every statement that anybody ever makes is made in answer to a question.

When I speak of statements I do not mean only statements made out loud to somebody else; I include statements made by somebody to himself in the course of solitary thinking. Similarly when I speak of questions I do not mean only questions asked him by somebody else; I include questions asked him by himself.

The reader’s familiarity with the truth expressed in this proposition is proportional to his familiarity with the experience of thinking scientifically. In proportion as a man is thinking scientifically when he makes a statement, he knows that his statement is the answer to a question and knows what that question is. In proportion as he is thinking unscientifically he does not know these things. In our least scientific moments we hardly know what the thoughts we fish up out of our minds are answers to questions at all, let alone what questions these are. It is only by analyzing the thought which I expressed by saying ‘this is a clothes-line’ that I realize it to have been an answer to the question ‘what is that thing for?’ and come to see that I must have been asking myself that question although at the time I did not know I was asking it.

Note. A question is logically prior to its own answer. When thinking is scientifically ordered, this logical priority is accompanied by a temporal priority: one formulates the question first, and only when it is formulated begins trying to answer it. This is a special kind of temporal priority, in which the event or activity that is prior does not stop when that which is posterior begins. The act of asking the question begins and takes a definite shape as the asking of a determinate question before the act of answering it begins; but it continues for the whole duration of this latter. Unless the person who answered a question were still going on asking it while he formulated the answer, he would have ‘lost interest in the subject’, and the ‘answer’ would not have been an answer at all. It would have been a meaningless form of words. By being answered a question does not cease to be a question. It only ceases to be an unanswered question.

Def. 1. Let that which is stated (i.e. that which can be true or false) be called a proposition, and let stating it be called propounding it.

Note. This is an arbitrary use of the words. In English usage a question or supposition is, equally with a statement, said to be ‘propounded’, and the word ‘proposition’ is not exclusively used for that which is stated. I adopt it here, warning the reader that it is jargon, because it is customary among logicians.

Prop. 2. Every question involves a presupposition.

It may be doubted whether any question that was ever asked involved one presupposition and no more. Ordinarily a question involves large numbers of them. But a distinction should be made between what a question involves directly and what it involves indirectly. Directly or immediately, any given question involves one presupposition and only one, namely that form which it directly and immediately ‘arises’ (see Def. 2). This immediate presupposition, however, has in turn other presuppositions, which are thus indirectly presupposed by the original question.

Unless this immediate presupposition were made, the question to which it is logically immediately prior could not be logically asked. Verbally, no doubt, it might be asked. There is no verbal impossibility in the way of asking a man whom you suppose to be an indulgent husband whether he has stopped beating his wife. But there is a logical impossibility; for that question arises from the presupposition that he has been in the habit of beating her. If he is not supposed to have been in that habit, the question whether he has stopped ‘does not arise’.

Def. 2. To say that a question ‘does not arise’ is the ordinary English way of saying that it involves a presupposition which is not in fact being made.

A question that ‘does not arise’ is thus a nonsense question: not intrinsically nonsensical, but nonsensical in relation to its context, and specifically to its presuppositions. A person who asks another a question which ‘does not arise’ is talking nonsense and inviting the other to talk nonsense in the same vein.

As one can ask questions without knowing it, and a fortiori without knowing what questions one is asking, so one can make presuppositions without knowing it, and a fortiori without know what presuppositions one is making. When I ask ‘What is that thing for?’ I need not be aware that I am presupposing that it is ‘for’ something. It is only in proportion as I am thinking scientifically that I take trouble to make myself aware of this. For example, when I am trying to decipher a worn and damaged inscription I know very well that before I begin answering the question ‘What does that mark mean?’ I must first assure myself that the mark is not accidental but is part of the inscription; that is to say, I must first answer the question ‘Does it mean anything?’ An affirmative answer, i.e. the statement ‘That mark means something’, causes the question to arise, ‘What does it mean?’

Def. 3. The fact that something causes a certain question to arise I call the ‘logical efficacy’ of that thing.

The question ‘What does that mark mean?’ would equally have been caused to arise if I had not stated but only ‘assumed’ or ‘supposed for the sake of argument’ that it means something; and this is what, like any other epigraphist, I do when I find myself unable to give a definite answer to the question whether a certain mark is part of the inscription or not. The logical efficacy of the supposition that the mark means something is identical with the logical efficacy of the proposition that it means something.

Def. 4. To assume is to suppose by an act of free choice.

A person who ‘makes an assumption’ is making a supposition about which he is aware that he might, if he chose, make not that but another. All assumptions are suppositions, but all suppositions are not assumptions; for some are made altogether unawares, and others, thought the persons who make them may be conscious of making them, are made without any consciousness of the possibility, if it is a possibility, that others might have been made instead. When correctly used, the word ‘assumption’ is always used with this implication of free choice, as when it is said ‘let us assume x = 10’. Sometimes it is in correctly used of malice prepense, by way of an insult; as when a man says to another with whom he is arguing, ‘you are assuming that no one will work except for payment’, where the point is that no one but a fool would make that assumption, though it is a supposition that might easily be made unawares. Similarly a man who wishes to be insulting may ask ‘What do you mean by treading on my toe?’ knowing perfectly well that the treader meant nothing by it, because he did not do it on purpose.

Prop. 3. The logical efficacy of a supposition does not depend upon the truth of what is supposed, or even on its being thought true, but only on its being supposed.

The point has already been made clear in discussing the previous proposition. It is a matter of common knowledge in the conduct of scientific thinking; where it is possible and often profitable to argue from suppositions which we know to be false, or which we believe to be false, or concerning which we have neither knowledge nor belief as to whether they are false or true. These doubts or negations in no way affect the validity of the argument.

The point is no less familiar in the conduct of practical affairs than it is in the conduct of scientific thinking. A man (or at any rate an intelligent man) does not regard himself as insulted if some one who has paid him a sum of money asks him for a receipt, or if the family of a lady whom he is about to marry proposes that a marriage settlement should be drawn up. He knows that the request or proposal is based on the assumption that he is capable, or will one day become capable, of acting dishonourably; but though he knows people assume this he does not necessarily think they believe it. He finds no difficulty in his distinguishing between their supposing him a rascal and their believing him one, and he does not regard the former as evidence of the latter.

Prop. 4. A presupposition is either relative or absolute.

In this context the word ‘presupposition’ refers not to the act of presupposing but to that which is presupposed.

Def. 5. By a relative presupposition I mean one which stands relatively to one question as its presupposition and relatively to another question as its answer.

Thus, if I do a piece of surveying in the course of which I take some hundreds of measurements with my old 66-foot tape, every time I ask any question in the form ‘What is the distance between these two points?’ I presuppose that the answer as given by a reading on my tape will be the right answer: that is, I presuppose that my tape is within a certain percentage of the length which it professes to be. But this is only a relative presupposition. A tape by a reputable maker is not likely to have been made grossly inaccurate in the first instance; but it is quite likely to have stretched during years of service in all weathers; and a sensible man will check it from time to time against something not liable to that accident, for example a surveyor’s chain. The accuracy of the tape, which while I am using it is a presupposition of the questions I ask, is one of the two possible answers, the affirmative answer, to the question I ask while I am thus checking it.

A man may use a measuring-tape without its ever occurring to him that the question of its accuracy might be raised. In that case his assumption of its accuracy remains unquestioned, and one might suppose that this fact removed it from the sphere of relative presuppositions as above defined. But this would be a mistake. That a certain conclusion follows from certain premises is not disproved by the fact that some one who states the premises fails to see that the conclusion follows. Similarly, that certain presuppositions are questionable is not disproved by the fact that some one who makes them fails to see that they are questionable. The business of logical inquiries, like that on which we are now engaged, is to study high-grade or scientific thinking: their conclusions are not impaired by the fact that low-grade or unscientific thinking also exists.

To question a presupposition is to demand that is should be ‘verified’; that is, to demand that a question should be asked to which the affirmative answer would be that presupposition itself, now in the form of a proposition. To verify the presupposition that my measuring-tape is accurate is to ask a question admitting of the alternative answers ‘the tape is accurate’, ‘the tape is not accurate’. Hence to speak of verifying a presupposition involves supposing that it is a relative presupposition.

Def. 6. An absolute presupposition is one which stands, relatively to all questions to which it is related, as a presupposition, never as an answer.

Thus if you were talking to a pathologist about a certain disease and asked him ‘What is the cause of the event E which you say sometimes happens in this disease?’ he will reply ‘The cause of E is C’; and if he were in a communicative mood he might go on to say ‘That was established by So-and-so, in a piece of research that is now regarded as classical.’ You might go on to ask: ‘I suppose before So-and-so fount out what the cause of E was, he was quite sure it had a cause?’ The answer would be ‘Quite sure, of course.’ If you now say ‘Why?’ he will probably answer ‘Because everything that happens has a cause.’ If you are importunate enough to ask ‘But how do you know that everything that happens has a cause?’ he will probably blow up right in your face, because you have put your finger on one of his absolute presuppositions, and people are apt to be ticklish in their absolute presuppositions. But if he keeps his temper and gives you a civil and candid answer, it will be to the following effect. ‘That is a thing we take for granted in my job. We don’t question it. We don’t try to verify it. It isn’t a thing anybody has discovered, like microbes or the circulation of the blood. It is a thing we just take for granted.’

He is telling you that it is an absolute presupposition of the science he pursues; and I have made him a pathologist because this absolute presupposition about all events having causes, which a hundred years ago was made in every branch of natural science, has now ceased to be made in some branches, but medicine is one of those in which it is still made.

Absolute presuppositions are not verifiable. This does not mean that we should like to verify them but are not able to; it means that the idea of verification is an idea which does not apply to them, because, as I have already said, to speak of verifying a presupposition involves supposing that it is a relative presupposition. If anybody says ‘Then they can’t be of much use in science’, the answer is that their use in science is their logical efficacy, and that the logical efficacy of a supposition does not depend on its being verifiable, because it does not depend on its being true: it depends only its being supposed (prop. 3).

Prop. 5. Absolute presuppositions are not propositions.

This is because they are never answers to questions (def. 6); whereas a proposition (def. 1) is that which is stated, and whatever is stated (prop. 1) is stated in answer to a question. The point I am trying to make clear goes beyond what I have just been saying, viz. that the logical efficacy of an absolute presupposition is independent of its being true: it is that the distinction between truth and falsehood does not apply to absolute presuppositions at all, that distinction being (see def. 1) peculiar to propositions.

Putting the same point differently: absolute presuppositions are never (see def. 1) propounded. I do not mean that they sometimes go unpropounded, like the so-called ‘propositions’ of the fashionable modern logic, which are called propositions even when nobody in fact propounds them, and would on that account be more accurately called ‘proponibles’; I mean that they are never propounded at all. To be propounded is not their business; their business is to be presupposed. The scientist’s business is not to propound them but only to presuppose them. The metaphysician’s business, as we shall see, is not to propound them but to propound the proposition that this or that one of them is presupposed.

Hence any question involving the presupposition that an absolute presupposition is a proposition, such as the questions ‘Is it true?’ ‘What evidence is there for it?’ “How can it be demonstrated?’ ‘What right have we to presuppose it if it can’t?’, is a nonsense question.

Hence, too, it is nonsense to say, as some modern logicians do say, that supposing is one of various ‘attitudes’ which we can take up towards a proposition, where a proposition means something which can be either true or false. This is merely a device for imposing on unwary readers the dogma, of which more will be said hereafter, that all presuppositions are relative, or that there are no absolute presuppositions.

More here and here.