Absence of Evidence

In the comments thread to a post on another blog, a commenter gave the following quotation:

'The simplest explanation for the total absence of evidence for gods is a total absence of gods'.

I've increasingly over the past couple of years come across claims of this sort (the commenter seems to be quoting someone, but I don't know who), and I find it interesting because the underlying idea seems to be pretty clearly wrong, for all its superficial plausibility, even when we ignore the obvious hyperbole of 'total absence of evidence'. (Obviously there's evidence -- religious experiences, etc.; the question is just whether it's adequate to establish the conclusion. It is very rare to find cases of actual disputes where one side literally has no evidence at all, inconvenient as that fact may be. Even believers in house elves have strange occurrences to call to witness. What we usually mean is that the evidence is weak, which is very different from being nonexistent. The rhetorical advantages of conflating weak evidence with no evidence are, of course, obvious; but we should not treat a rhetorical figure as literal speech.) What we mean by "total absence of evidence" is at most a total absence of evidence available to be used in reasoning (otherwise the only way to establish total absence of evidence for X is to prove that X can't possibly exist -- if we aren't talking about evidence available to us, we'd have to take into consideration all evidence available to everyone at every time, including the future, and therefore we would need to establish a guarantee that no real evidence could possibly turn up in the future). And because of this, if all other things are equal, the simplest explanation for absence of evidence is that you've probably just overlooked it or not come across it. It is simplest in at least three different ways:

(1) It involves the weakest supposition about the world. If I commit to the claim that some evidence of X probably exists, I'm not by that committed to any claim for or against the existence of X, just to the existence of something that someone could reasonably classify as evidence for the existence of X, whatever that evidence might be. This is clearly a weaker supposition, with fewer commitments, than the supposition that there is no X.

(2) It is the simplest in that, unlike a categorical rejection or affirmation of something's existence, it allows for the subsumption of the case under an already well-established generalization, that is, the straight psychological fact that people often overlook or fail to come across evidence for things.

(3) It is the simplest in that it provides the least impediment to future inquiry: it closes down the fewest options for further research.

Part of the problem, I think, is that phrases like 'total absence of evidence for the existence of X', despite the literal meaning, actually convey in practical, colloquial speech the idea that there is, overwhelmingly, evidence against the existence of X, and it is indeed true that the simplest explanation for overwhelming evidence against the existence of X is X's nonexistence. And perhaps a failure to recognize that we do not, in actual practice usually judge absence of evidence absolutely but relative to what is accessible to us (the distinction I mentioned above) contributes to this confusion. But what is actually happening is that an entire range of suppositions is being elided. And there's a reason why people often say that absence of evidence is not evidence of absence: it's precisely that actual absence of the thing/event/whatever is not the simplest explanation for absence of evidence, considered on its own.

There are actual cases where an absence of evidence would be evidence of absence, of course; the cases, that is, where all other things are not equal. In practice, all of these are cases where we actually have pre-existing preponderant reason (either through preponderance of evidence or through actual proof) that X's existence is inconsistent with the lack of evidence in question, or else made definitely unlikely by it, and that it is either impossible or unlikely that the reason the evidence is lacking is your fault. But these cases, of course, don't salvage the general principle.

Chrysorrhoas

Today is the Feast of St. John of Damascus. John was a Syrian Christian; his name at birth may have been Mansur ibn Sarjun al-Taghlibi -- our records are not wholly clear, and if I understand correctly it is possible that this was really the name of his father. The family of Mansur was a family of fair local importance in a time of great change: John's grandfather was in charge of taxes under the Byzantine Empire, and then, when the region was conquered by the Umayyad caliphate, the family continued in the civil service, working for the caliph (which was common among the civil servants of the time). Indeed, John's father, Sarjun, was put in charge of building the Arab fleet for the purpose of attacking Constantinople. John himself served in the court of the caliph for some time, before going to the Mar Saba monastery. It was there, at Mar Saba, that he took the name John as his monastic name. He wrote quite a few important works, the most important of which is the one usually known in the west as the Exposition of the Orthodox Faith. Because he's primarily a synthesizer of doctrine, his creativity is often overlooked; as with most synthesizing geniuses, the creative ingenuity he constantly displays is not flashy and obvious but often very subtle. He is sometimes called Chrysorrhoas, which means, "streaming with gold."

Tolstoy's cousin, Count Alexei Tolstoy, wrote a poem about John of Damascus that became the core of a famous cantata by Taneyev, Ioann Damaskin, also sometimes called A Russian Requiem. It is Russian music at its finest, and streaming with gold itself. The following is but an excerpt (the third movement).

Make Plain My Pathway Still

O Thou Essential Word
by Catherine Winkworth

O Thou essential Word,
Who wast from the beginning
With God, for Thou wast God;
Thou hope of all the sinning,
Chosen to save our race,
Welcome indeed Thou art,
Redeemer, Fount of grace,
To this my longing heart.

Come, self-existent Word,
And speak Thou in my spirit!
The soul where Thou art heard
Doth endless peace inherit.
Thou Light that lightenest all,
Abide through faith in me,
Nor let me from Thee fall,
And seek no guide but Thee.

Ah! what hath stirred Thy heart,
What cry hath mounted thither,
And reached Thy heavenly throne,
And drawn Thee, Savior, hither?
It was Thy wondrous love,
And my most utter need,
Made Thy compassions move,
Stronger than death indeed.

Then let me give my heart
To Him who loved me, wholly;
And live, while here I dwell,
To show His praises solely;
Yes, Jesus, form anew
This stony heart of mine,
Make it till death still true
To Thee, for ever Thine.

Let nought be left within
But what Thy hand hath planted;
Root out the weeds of sin,
And quell the foe who haunted
My soul, and set the tares;
From Thee comes nothing ill,
O save me from his snares,
Make plain my pathway still.

Thou art the Life, O Lord,
And Thou its Light art only!
Let not Thy blessèd rays
Still leave me dark and lonely.
Star of the East, arise!
Drive all my clouds away,
Till earth’s dim twilight dies
Into the perfect day!

Winkworth, one of the very small handful of hymn-translators to rival John Mason Neale in importance and quality, is here translating a German hymn by Laurentius Laurenti.

Cogito Ergo Sum XII

Descartes, Second Replies (CSM II, 104):

Now some of these perceptions [of the intellect] are so transparently clear and at the same time so simple that we cannot ever think of them without believing them to be true. The fact that I exist so long as I am thinking, or that what is done cannot be undone, are examples of truths in respect of which we manifestly possess this kind of certainty. For we cannot doubt them unless we think of them; but we cannot think of them without at the same time believing they are true, as was supposed. Hence we cannot doubt them without at the same time believing they are true; that is, we can never doubt them.

Cogito Ergo Sum XI

Descartes, Second Replies (CSM II, 140):

When someone says 'I am thinking, therefore I am, or I exist', he does not deduce existence from thought by means of a syllogism, but recognizes it as something self-evident by a simple intuition of the mind. This is clear from the fact that if he were deducing it by means of a syllogism, he would have to have had previous knowledge of the major premiss 'Everything which thinks is, or exists'; yet in fact he learns it from experiencing in his own case that it is impossible that he should think without existing.

Philosophical Folklore

As some long-term readers know, I have an interest in philosophical folklore; much of this folklore is found in discussions of critical thinking and informal logic, which is a pretty fruitful hunting ground for it: almost everything that goes by the name 'critical thinking', and much in the field of informal logic, is philosophical folklore, bits and pieces that have filtered down and become common legend. Some of these bits and pieces, used wisely, do good work; others are, as we might say, mere superstition -- things that were once held by only a few for very specific and very controvertible reasons, or things that have long since become too crudely simplified to do the work they are supposed to do, or things that once made good sense but are now consistently understood a completely different way due to the accidents of linguistic change.

But one finds philosophical folklore elsewhere, especially when it comes to history of philosophy. I've mentioned, for instance, the irony that what is often called Leibniz's Law is not found in Leibniz; you can find superficially similar claims, but on closer claim they turn out not to have anything to do with identity in the proper sense, or else to be obviously different in logical character from what goes by the name. For instance, Leibniz explicitly tells us that his claim in Discourse on Metaphysics, section 9, which is often said to be the source, is paradoxical, in the company of claims like "You can't divide substances in half" or "Every substance mirrors the entire world." It's also based purely on Leibniz's very peculiar account of what an individual substance is. Nothing like this is even remotely in view when people talk about "Leibniz's Law". In this case what seems to have happened is that some claims made by Leibniz were put into a very different logical form than Leibniz himself would or could have put them, and by people making assumptions Leibniz himself wouldn't or couldn't have made, with the result that things were changed significantly in the translation.

Another example is that what is usually called Pascal's Wager actually does not derive directly from Pascal, although it was influenced by him. It really derives from Arnauld and Nicole's Port-Royal Logic and you can recognize it by the fact that it gives a role in the Wager to hell -- i.e., very bad consequences play an important role in the argument. This is not the way Pascal sets up his own Wager, in any of the fragments we have. What happened there is that Port-Royal Logic was published long before anything directly from Pascal (we only have Pascal's version in fragmentary notes published posthumously), and therefore it had a chance to become very widespread, although, since it clearly is influenced by Pascal, it gets Pascal's name.

Another example, about which I've been meaning to write a post (but it's a complicated issue and so I need to have a good stretch of time to do it), has to do with the phrase "Knowledge is Power". It's usually attributed to Francis Bacon. It is indeed a very Baconian sentiment, and Bacon does have the Latin phrase scientia est potentia in his writings. But there he's talking about divine simplicity, and the claim he is making is that knowledge is (the same as) power for God, as opposed to us. One occasionally also finds it attributed to Thomas Hobbes, and indeed, Thomas Hobbes also says that knowledge is power; and the meaning is much more like what we usually mean by it. But he adds sed parva, roughly, "but only a little", and that's a pretty important qualification.

The list could be extended at considerable length. Not all bits of philosophical folklore are wrong, it should be said, although explaining the ones that are wrong is often a more interesting task than explaining the ones that are right. And even those that are wrong if taken straight may nonetheless show some real insight -- "knowledge is power" is indeed a pretty good summary of Baconian philosophy, even if Bacon never thought to summarize it exactly that way, and it would be virtually impossible to come up with a three-word summary that does better -- or be based on conflations or errors that even very reasonable people may make.

What sets me in mind of all this is this discussion of a bit of philosophical folklore, by T. H. Irwin. One occasionally encounters the claim that Augustine argued that the virtues of pagans were merely 'splendid vices', splendida peccata. As with most such philosophical folklore, one can make some Augustinian sense of the claim (although, as Irwin notes in the paper, how much Augustinian sense is a tricky matter to determine, with lots of room for controversy); but Augustine himself seems never actually to say this. This is a particularly interesting case because it has been a massively influential bit of philosophical folklore. Because philosophical folklore is popular and widely accepted, it does tend to have some real influence, which is why it's very worthwhile for historians of philosophy like myself to study it (and a real shame that we don't do it more often). But the degree of influence of this particular tidbit through history has been quite extraordinary; there are probably only a relatively small handful of folkloric tidbits (like Ockham's Razor) that have been more influential.

Cogito Ergo Sum X

Descartes, Meditations on First Philosophy, Meditation Two:

But how do I know that there is not something different altogether from the objects I have now enumerated, of which it is impossible to entertain the slightest doubt? Is there not a God, or some being, by whatever name I may designate him, who causes these thoughts to arise in my mind? But why suppose such a being, for it may be I myself am capable of producing them? Am I, then, at least not something? But I before denied that I possessed senses or a body; I hesitate, however, for what follows from that? Am I so dependent on the body and the senses that without these I cannot exist? But I had the persuasion that there was absolutely nothing in the world, that there was no sky and no earth, neither minds nor bodies; was I not, therefore, at the same time, persuaded that I did not exist? Far from it; I assuredly existed, since I was persuaded. But there is I know not what being, who is possessed at once of the highest power and the deepest cunning, who is constantly employing all his ingenuity in deceiving me. Doubtless, then, I exist, since I am deceived; and, let him deceive me as he may, he can never bring it about that I am nothing, so long as I shall be conscious that I am something. So that it must, in fine, be maintained, all things being maturely and carefully considered, that this proposition I am, I exist, is necessarily true each time it is expressed by me, or conceived in my mind.