I began by admiring Hume's naive liberalism, his supposition that there could be a free (i.e. unrestricted) opposition of sentiments and arguments without disturbing the underlying consensus of meaning which any discussion requires.   This belief fits well the study of Philosophy within a public institution, where discussion is as free as it likes so long as it has no immediate bearing on the context within which it is discussed.   He leaves out, as it were, the social significance – the significance for academic politics.   Surely, I wanted to ask Hume, he would agree that a professor would be right in refusing to accept a thesis which totally rejected the way Philosophy was conducted at his university, even though the professor could not refute its arguments.

Perhaps Hume would reply that such a thesis could no more be argued for than refuted on philosophic grounds, where the context is looser than that of an academic institution.   But even Hume may recognize at this point that there is a problem of meaning here, that if words have no power then they can have no meaning; freedom of speech is not much use if nothing one says has any effect.   Indeed, Hume certainly appears to regard the nature of Philosophy as a philosophic concern, and this concern would seem to extend to arguments for his particular conception of Philosophy.   I do not wish to be accused of attributing to Hume views which he may reject within the novel context in which I here present them.   Let me therefore construct a character called Emuh to serve the purpose of this discussion.

Let us therefore suppose Emuh to hold that Philosophy is the completely untrammelled opposition of sentiments and arguments, the naive liberalism just discussed.   And to give the discussion a focus, I, his audience, will take the opposing view, viz. that there is a single theory that explains everything.

EMUH:   We shall not here dispute concerning the content of the theory of everything which you claim to have.   We shall only enquire how far any content it may have might affect the nature of philosophic debate.   I will show the content to be entirely indifferent to the calm of rational discussion and security of scientific progress.

You indulge a rash curiosity in trying to establish Philosophy upon what can be written down alone; and you thereby excite, instead of satisfying, the doubts, which naturally arise from diligent enquiry and close scrutiny.   You paint a metaphysical picture in the most magnificent colours, the order, beauty and subtle interplay of ideas; and then ask if such a glorious display of intelligence could not have something going for it.   But I do not wish to examine the validity of this argument in the present discussion.

MYSELF:   In the sense that everything true must be contained in a theory of everything, dispute concerning the content of the theory must necessarily arise in any dispute between us.   But for the sake of engaging you in free debate, I will not insist that you acknowledge there is, or even might be, a theory of everything until you yourself should freely recognize that you have assumed all along (unwittingly) that there is such a theory.

I shall not, therefore, try to elaborate and defend in a direct manner the argument which you have just summarily sketched.   Indeed I will admit that the only arguments acceptable as philosophic must be derived from trying to explain something there to be explained; I hold the fact of already having explanations justifies supposing that there are further things waiting to be explained, and that it is worth seeking explanations rather than resigning oneself to meaninglessness or the mouthing of sentiments and the conforming to social conventions without conviction.

EMUH: You will allow that such arguments must proceed from that explained to the explanation.   From the explanations you bring forward you infer that the theory was already there implicit in that explained waiting for you to make it explicit.   If your theory was not already there you must allow that your conclusion fails; and you do not claim to establish the theory as something containing anything more than the phenomena it explains will justify.

No explanation can be allowed to ascribe any qualities except those which belong to that explained. (Metaphors must be qualified as such.)   If any explanation should be inadequate, we must either reject it, or add such qualities as will match that explained.   But if we ascribe further qualities than can be justified in that explained, then we must be prepared to amend the explanation.

MYSELF:   In general, an explanation does not add to the thing explained, but only to our understanding of the thing.   But what if that explained cannot be separated from any attempt by us to explain it, so that as we discuss it, we are adding to what was originally there to be explained?   Such is indeed the case for explanations about explanations in general.

EMUH:   My point is simply this.   Allowing that your theory explains all we are familiar with, we cannot then deduce that it can explain all that has yet to come to our notice.   From its success in explaining what we know, we cannot deduce that it can explain what we do not know – it cannot be the foundation of any new knowledge or understanding.

You find certain phenomena.   You seek an explanation.   You imagine you have found one.   You afterwards become so enamoured of the fruit of this virginal conception, which the midwife Socrates has helped you to bring to birth, that you imagine it impossible, but that it must explain everything, so that the present disorder and meaninglessnes is mere illusion.   You forget that the claim to explain everything is not justified; and that you have no ground to ascribe to the theory any qualities but what you see it actually has, that you should not claim that it offers explanations which are not yet displayed in its exposition.   So you should let your theory be suited to the present appearances of things; and presume not to alter these appearances by arbitrary suppositions, so as to credit the theory with explaining everything.

How can any philosophic theory contain anything about what will happen or explain any anything beyond what has actually appeared?   If you tell me that you have gradually ascended by reason and by finding explanations of explanations, I still insist that you have aided the ascent of reason by the wings of imagination; otherwise you could not be arguing from your theory to things as yet unknown, forgetting that it only explains what we find now in the world at present.

MYSELF:   I agree that what you describe is a real psychological danger, the sin of pride.   But you misunderstand the way in which it arises.   Every explanation takes itself to be part of some theory of everything even when this is denied – denial indeed increases the danger, through forgetfulness, of presuming that the theory has been completely expounded (that the explanation undergoes no signficant change in being integrated into the theory).   Nobody who openly claims to explain everything is likely to get away with such presumption.

Perhaps we should focus on what is implicit in any explanation.   Let me ask you: Do you deny that we are able to find meaning, that we are able to explain things?

EMUH:   No, of course not.   I only deny that there is a theory that explains everything, a theory which sifts out sense from nonsense in all our attempts to explain.   I accept that being able to explain things and to reconcile explanations with one another are the chief intellectual joys of life.   I never accept meaning and nonsense on an equal footing, that the latter only acquires value indirectly either as comic relief or as a byproduct of intellectual exploration.

MYSELF:   The ability to explain presupposes a theory of everything.

EMUH:   But whatever it presupposes, the ability itself, on which depends our ability to converse with one another, and consequently our conduct in life, is what we are agreeing on and arguing from.   It is still open for me, as well as for you, to guide the development of my understanding, according to what I have already learnt.   And if you affirm that your theory is more comprehensive and absolute beyond what is possible in a finite exposition, you are making the same mistake as I have already pointed out.   You persist in imagining that, if we grant such a comprehensive theory is being expounded, you may safely infer consequences from the theory, and add something to that explained which cannot, as yet, be known by other means.   You forget that all your reasoning here can only be drawn from that explained, that which we already in some way know.   The theory must already be found to the full in that explained.

Instead of regarding the present scene of things as all that has to be explained, you have reversed the order of composition of explanations, rendering everything merely a shadow or reflection of your theory rather than vice versa, a Wittgensteinian ladder that you have kicked from under you (Tractatus Logico-Philosophicus, §6.54).   Whence, do you think, your idea of the theory derives?   From your own conceit and imagination surely.   For if you derived it from the present phenomena, it would never point to anything further, but must be exactly adjusted to them.   It is true your theory may possibly be more comprehensive than we could ever see demonstrated.   But still this is mere possibility and hypothesis.

To sum up, our public life together is the great standard, by which we all regulate our arguments and our understanding.   Nothing else can be appealed to in philosophic works.

MYSELF:   An appeal to our common life is one to which. I attach much importance.   But from this appeal it may be possible to refute your argument, though you claim to base your argument on it.   If you saw, for instance, a half-finished building, surrounded with heaps of brick and stone and mortar, and all the instruments of masonry; could you not infer from this that a building was being constructed?   And could you not return again from this inference and conclude that the building would soon be finished, and receive all the further improvements, which art could bestow upon it?

If you saw upon the sea-shore the print of one human foot, you would conclude that someone had passed that way and that she or he had also left traces of the other foot, though effaced by the rolling of the sands or inundation of the waters.

Why then do you refuse to admit the same kind of reasoning in the case of the theory?   Consider the exposition of the theory as only an unfinished building, from which you can infer an exposition more finished; and arguing from that exposition infer one yet more finished; and so on ad infinitum, eventually using every brick there is?

EMUH:   In explaining human activities, it is possible to turn back from the explanation to form new inferences concerning the activities being explained, and examine the alterations which the activities have probably undergone, or may still undergo.   This is because we know human beings by experience, whose motives and designs we are acquainted with, and those projects and inclinations have a certain connexion and coherence which we can establish.   When, therefore, we find, that any work has proceeded from the skill and industry of people; as we are otherwise acquainted with them, we can draw a hundred inferences concerning what may be expected from one work; and these inferences will all be founded in experience and observation.   But if we knew people only from the single work of production which we examine, it would be impossible for us to argue in this manner; because our knowledge of all the qualities which we ascribe to the person, being in that case derived solely from the one production, it is impossible they could point to anything further, or be the foundation of any new inferences.

The print of a foot in the sand can only prove, when considered alone, that there was some figure fitting it, by which it was produced; but the print of a human foot proves likewise, from other experience, that there was probably another foot, which also left its impression, though effaced by time or other accidents.   Here we mount from that being explained to the explanation; and, descending again from that explanation, infer that additional things are explained; but this is not a continuation of the same simple chain of reasoning.   We comprehend in this case a hundred other explanations within our particular one.

The case is not the same for your theory.   In embracing every other possible explanation (there can be no way of standing outside it and making a critical assessment of it) there can be no other explanations we can bring to it so that we can add to that explained.   Every new phenomenon implies an addition to that which must be explained by the theory, but there is no way of extending the theory to cope with such additions.

MYSELF:   The main source of the difference between us in this matter is not that you fail to assume that you are contributing to the exposition of a comprehensive theory, but that you fail to recognise the fact – from the best of motives, I hasten to add.   You can contribute to something without ever intending to do so, but in the present discussion I must assume something about your intentions if I am to have a chance of winning you over.   This assumption cannot be based on any particular experience I have of you, as if you were certain, on every occasion, to observe the same conduct, which I, in your situation, would have embraced as reasonable and available as an option.   For, besides the ordinary course of experience being different for you, and besides the possibility that almost everything in your life may be regulated by principles and maxims very different from mine, we are ourselves both like unfinished buildings, and our common life also.

Our common life is not something merely given to us, but something we are living; nor is it merely self-sustaining, but something we are nourishing in each other.   I might not be able to deduce, as a disinterested observer, that a half-finished building will be completed.   It might be that the surveyor overlooked a nuclear waste dump underneath the site, and the workmen, when they discover this, will immediately abandon the site, refusing even to remove the unused building materials for fear of radiation.   But, as a bricklayer working on the site, would I be inferring merely from my experience on other building sites that a building was being constructed?   Can I not infer it as an assumption implicit in my actions, without which my actions cease to be rational?   In the same way the theory of everything is implicit in any rational reflection, i.e. any discussion about explanations.

EMUH:   You have yet to show that to be necessarily the case.   Besides, can making explicit the assumption about the theory of everything ever make any difference to our explanations?   Philosophy will never be able to carry us beyond ourselves, or give us measures of argument and truth not based on reflection on common life.   No new fact can be inferred from your hypothetical theory, no prescribing of meaningfulness beyond what is already found by general social intercourse.   Your theory can have no effect on anything.

MYSELF:   So long as the notion that there is a theory of everything remains an abstract notion, then clearly it can have no effect on anything.   But if the theory is being expounded somewhere, then it can be said to affect things through its exposition.   Other explanations can then be transformed in their significance by making explicit the assumption about the theory, for this explicitness relates them to the exposition.

And this leads me to an answer to your main point.   In "mounting" from the evidence of the footprint to the belief that there was another footprint now erased we are indeed relating a hundred other explanations from other contexts within our particular one.   The same can also be true of a theory of everything: every explanation can be related to its particular exposition by exposing how the theory is implicit in it.   I agree, as you seem to take for granted, that a theory of everything must be unique ("singular and without parallel"), but its uniqueness is like that of a person.   And we do not have only a single production, its direct exposition, but the whole history of Philosophy.

This conversation, like all good conversations, must be broken off just as it seems to be getting most interesting, so as to be sure of provoking further discussion at a later date.