“When you have eliminated all which is impossible, then whatever remains, however improbable, must be the truth.” So said Sherlock Holmes. It is a fine maxim, particularly for a detective endowed with almost supernatural powers of investigation, but it does assume the validity of the method of elimination. If we employ a method which eliminates all possibilities but one, leaving us a single conclusion that is so outlandish and improbable that it beggars belief, we might question our method before we accept the conclusion.

Thus we may use the consequences of a philosophical argument as a heuristic guide to the argument’s validity. It must be emphasised that such an approach is only a guide; it is an optimisation of the algorithm we use to assess all those philosophies which we encounter. There are so many different philosophical arguments that we do not have the time, or the inclination, to carefully analyse them all. Instead, we use a simple heuristic to choose those worthy of closer investigation and discard those unlikely to be of merit.

I have not taken the time to carefully investigate the philosophy of Jim Jones, as the actions of Jones and his followers are enough to put me off. That is to say, the consequences of his philosophy are such that I can, with a reasonable degree of confidence, dismiss the philosophy itself without actually taking the time to analyse it.

This sort of quick test – a glance at the consequences in lieu of analysis of the substance – is fairly common. It is a sensible and practical way to dismiss the outlandish and thus focus on the reasonable. It is not foolproof – many things that are obvious today were once thought to be ridiculous – but it is pretty good. The outlandish may turn out to be correct but it is not unreasonable to demand more compelling evidence in favour of a very strange claim than one might demand in favour of a commonplace claim.

The success of this method as a heuristic optimisation might suggest its use elsewhere. Perhaps, if the consequences of an argument are in some sense unacceptable, we might reject that argument not because we do not have the time or inclination to investigate but rather despite our investigations. We may be unable to clearly express a logical refutation of the argument and yet nevertheless refute it on the grounds that its conclusion is absurd.

Here we are on dangerous ground. It is necessary to be very cautious when condemning a consequence as unacceptable or absurd. Unacceptable according to whom? Why? Is it as absurd as the idea of a spherical Earth seemed thirty centuries ago?

However, there is still some heuristic value in the approach, as long as we remember that it is but a guide and cannot be conclusive itself. Consider solipsism. Within its own logical framework, it is very hard to disprove solipsism. It is internally consistent and, rather trivially, accords with all experience. However, it is plainly nonsense.

Solipsism is an excellent example of a philosophical position arrived at by following a logical train of thought from plausible assumptions which is nevertheless implausible itself. When confronted by a solipsist we may be unable to logically refute his philosophy but we may still reject it.

Wikipedia puts it thus:

A subjective argument for the implausibility of solipsism is that it goes against the commonly observed tendency for sane adult humans in the western world to interpret the world as external and existing independent of themselves. This attitude, not always held by children, is listed by developmental psychologists as one of the signs of the maturing mind. The principle is deeply held, and well integrated with human languages and other thought processes. However, that humans think this way, even if they must think this way, does not prove something true.

We cannot prove it is false but it is so completely opposed to our most basic modes of thought that even if it were true we must continue as if it were not.

I feel much the same way about nihilism.

Hume is credited as the first philosopher to point out the fallacy of deriving ought from is:

In every system of morality, which I have hitherto met with, I have always remark’d, that the author proceeds for some time in the ordinary ways of reasoning, and establishes the being of a God, or makes observations concerning human affairs; when all of a sudden I am surpriz’d to find, that instead of the usual copulations of propositions, is, and is not, I meet with no proposition that is not connected with an ought, or an ought not. This change is imperceptible; but is however, of the last consequence. For as this ought, or ought not, expresses some new relation or affirmation, ’tis necessary that it shou’d be observ’d and explain’d; and at the same time that a reason should be given; for what seems altogether inconceivable, how this new relation can be a deduction from others, which are entirely different from it.

Hume was one of the first philosophers, if not the first philosopher, to develop an entirely naturalistic philosophical system. Naturalistic philosophers hold that all truths are truths of nature: that is to say, nature, the material, physical world is all that there is and thus all true statements are or can be derived from physical facts. Hume rejected the philosophies of his more religiously inclined predecessors, who dealt with metaphysics and invoked the supernatural, in favour of empiricism and naturalism.

As far as I can see, this leaves us with only three possibilities:

  1. Moral propositions cannot be objectively true. At best they can only be true in some subjective, relativistic sense, which is to say that all moralities are equally true, which is the same as saying that none are true, which is to say that there is no morality. This is nihilism.
  2. Hume was wrong to claim that moral propositions, those concerning ought, cannot be deduced from physical propositions, those concerning is. In fact we can use a naturalistic methodology, perhaps the scientific method, to deduce morality.
  3. Hume’s naturalism is wrong. Nature is not all that there is and not all truths are natural truths. Thus ought cannot be derived from statements of physical truth but it can be derived from another truth, for all that is is not physical.

The first option I reject for the same reason that I reject solipsism. I do not do so with the same vehemence that I reject solipsism for I recognise that I am on shakier ground here. However, on balance I believe I am correct to reject any proposition that entails nihilism.

The second option is tricky. A number of people have attempted to deduce morality from physical truth but I have yet to be convinced. Of all the attempts that I have encountered, I am most impressed by that of Robert A. Heinlein. I intend to investigate Heinlein’s morality, as expressed in his speech to graduating midshipmen at the US Naval Academy, published as The Pragmatics of Patriotism, in a later article on this blog. His argument appeals to me greatly but I suspect that it is logically flawed. We shall see.

Which leaves us with the third option. I have been pondering this one for a long time and still don’t know what to say about it. The problem with refuting metaphysical naturalism is that I cannot deny the success of methodological naturalism. The former does not logically follow from the latter, no matter how much some naturalist philosophers might want it to, but unless we augment our naturalistic method with some other method then it might as well do so. If we have no means of determining the truth of a non-physical proposition then it does us little good to claim that some truths are non-physical.

So we may disagree with the naturalist’s assertion that all truths are physical but unless we propose a methodology by which non-physical truths may be discovered then our disagreement is of little consequence. Traditionally, metaphysicians have relied on logic without experimental verification. I believe the argument goes something like this:

All rational philosophies, naturalism included, rely on certain fundamental assumptions. These assumptions, which we might think of as the axioms of a logical system, are not themselves amenable to experimental verification for the obvious reason that the validity of experiment as a means of verification is itself dependant on these axioms. To attempt to prove an axiom by means of itself is trivially invalid: it is circular reasoning.

I am reminded here of the failure of logical positivism. The logical positivists hoped to do away with metaphysics (and all other branches of philosophy that they deemed unscientific) by means of their Verification Principle. This principle held that a proposition is meaningless unless it can be empirically tested; that is, unless it can be verified by experiment. Unfortunately for the hopeful positivists, the principle is, according to itself, completely meaningless: there is no empirical test that might verify such a principle. In their desire to purge philosophy of metaphysics, the positivists ended up promoting a metaphysical principle.

Thus every rational philosophy, even those philosophies that would rather limit themselves to the empirical and naturalistic world of science, must necessarily accept some set of axioms without which logic and rational enquiry are impossible. It is therefore not the case that any rational philosophical system can truthfully claim to be entirely free of metaphysics.

We may therefore argue logically from these axioms themselves, perhaps but not necessarily with the aid of experimental observation, to reach metaphysical conclusions. Such conclusions would not be amenable to experimental verification or falsification (except insofar as they depend in part, as they may, on empirical observation) but we would nevertheless be able to decide between competing metaphysical claims by the method of logical analysis.

It may be noted that physics and metaphysics, on this account, are not so opposed as positivists may assume. The theories of physics, as we have seen, depend on metaphysical axioms no less than any other rational theories. (For example, the validity of deductive inference is assumed, as well as, perhaps, inductive inference.) We may reasonably say that the natural sciences assume a minimal set of axioms and from there on proceed on the basis of empirical verification or falsification, which places them at the extreme of a spectrum whose other extreme consists of solely logical argument with no reference to empirical observation whatsoever.

The above may help to demonstrate the fallacy of deriving metaphysical naturalism from merely methodological naturalism. However, we still face the challenge of deducing metaphysical truths, especially those concerning morality, either from that minimal set of axioms necessary to the natural sciences or from a larger superset consisting of that minimal set along with other axioms that we can reasonably justify.

This is not a simple task but it strikes me as more likely to succeed than the second option given above: the derivation of morality from physical truth alone. The first step, which I shall not attempt today, is surely the enumeration of axioms from which we may later proceed.

Published in: on May 13, 2009 at 12:31 am  Comments (2)  

2 CommentsLeave a comment

  1. Hello, I came to your blog through a comment you left on Edward Feser’s blog.

    This is a rich post, and I don’t have it in me to say much about it at the moment. (I think some people would say not Hume but Epicurus and his followers developed the first fully naturalistic worldview? Just something that I remember reading in the intro to a book on atheism called Varieties of Unbelief.)

    But I did want to mention a couple titles that are about what you asked about on the other blog, namely how the truth of a particular religion might be argued for. I only know of such works that argue for Christianity. I think someone mentioned William Lane Craig’s Reasonable Faith; it’s true that a part of that book argues for the historical reliability of the resurrection. That, from what I can tell, is the approach most Christian apologists take these days to arguing for the truth of Christianity: Jesus’ resurrection is the best explanation for the events of very early Christianity. And if Jesus rose, Christianity is true. That’s the argument.

    I think Gary Habermas, a biblical scholar, is one of the foremost experts in the field; he seems to have several books on the historical validity of Jesus’ resurrection. The same goes for the philosopher Richard Swinburne, who argues for the resurrection but also for Christianity more broadly speaking. A book called The Case for Christ edited by Lee Strobel brings together many essays arguing from different viewpoints for the Christian conception of the person of Jesus. I’ve heard people mention a slightly older book called More than a Carpenter by Josh McDowell in this context, but I’ve never looked at it myself.

    Anyway, I hope I understood your question, and best of luck in your studies!

  2. I wouldn’t call Epicurus’ philosophy naturalistic, although in some respects it might as well be. Epicurus bases his arguments about religion on the perfection of God: he is practically a Deist.

    Also, it is not clear (at least to me) that what the Greeks referred to as ‘physis’ is quite the same as what we today (or those in Hume’s day) would have called the physical or nature.

    However, I accept that the basic idea of discounting supernatural causes and seeking to explain all phenomena in terms of natural causes, for some understanding of the term ‘natural’, has been around since at least the Ancient Greeks. I merely claim that Hume was probably the first philosopher to articulate a coherent system of philosophy that we would today recognise as naturalistic.

    Thank you very much for those reading suggestions, they are much appreciated!

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