## Addendum on Existential Risk and Existential Uncertainty

### 23 April 2013

Tuesday

Earth and the moon in one frame as seen from the Galileo spacecraft 6.2 million kilometers away. (from Picture of Earth from Space by Fraser Cain)

In my post Existential Risk and Existential Uncertainty I cited Frank Knight’s distinction between risk and certainty and attempted to apply this to the idea of existential risk. I suggested that discussions of existential risk ought to distinguish between existential risk (sensu stricto) and existential uncertainty.

In Knight’s now-classic work Risk, Uncertainty, and Profit, Frank Knight actually made a threefold distinction in the kinds of probabilities that face the entrepreneur:

1. A priori probability. Absolutely homogeneous classification of instances completely identical except for really indeterminate factors. This judgment of probability is on the same logical plane as the propositions of mathematics (which also may be viewed, and are viewed by the writer, as “ultimately” inductions from experience).

2. Statistical probability. Empirical evaluation of the frequency of association between predicates, not analyzable into varying combinations of equally probable alternatives. It must be emphasized that any high degree of confidence that the proportions found in the past will hold in the future is still based on an a priori judgment of indeterminateness. Two complications are to be kept separate: first, the impossibility of eliminating all factors not really indeterminate; and, second, the impossibility of enumerating the equally probable alternatives involved and determining their mode of combination so as to evaluate the probability by a priori calculation. The main distinguishing characteristic of this type is that it rests on an empirical classification of instances.

3. Estimates. The distinction here is that there is no valid basis of any kind for classifying instances. This form of probability is involved in the greatest logical difficulties of all, and no very satisfactory discussion of it can be given, but its distinction from the other types must be emphasized and some of its complicated relations indicated.

Frank Knight, Risk, Uncertainty, and Profit, Chap. VII

At the end of the chapter Knight finally made his point fully explicit:

It is this third type of probability or uncertainty which has been neglected in economic theory, and which we propose to put in its rightful place. As we have repeatedly pointed out, an uncertainty which can by any method be reduced to an objective, quantitatively determinate probability, can be reduced to complete certainty by grouping cases. The business world has evolved several organization devices for effectuating this consolidation, with the result that when the technique of business organization is fairly developed, measurable uncertainties do not introduce into business any uncertainty whatever. Later in our study we shall glance hurriedly at some of these organization expedients, which are the only economic effect of uncertainty in the probability sense; but the present and more important task is to follow out the consequences of that higher form of uncertainty not susceptible to measurement and hence to elimination. It is this true uncertainty which by preventing the theoretically perfect outworking of the tendencies of competition gives the characteristic form of “enterprise” to economic organization as a whole and accounts for the peculiar income of the entrepreneur.

Frank Knight, Risk, Uncertainty, and Profit, Chap. VII

Knight’s distinction between risk and uncertainty — between probabilities that can be calculated, managed, and insured against and probabilities that cannot be calculated and therefore cannot be managed or insured against — continues to be taught in business and economics today. (It is a distinction closely parallel to Rumsfeld’s distinction between known unknowns and unknown unknowns, though worked out in considerably greater detail and sophistication.) Knight’s slightly more subtle threefold distinction among probabilities might be characterized as a tripartite distinction between certainty, risk, and uncertainty.

Knight acknowledges, in his account of statistical probability, i.e., risk, that there are at least two complications:

1. that of eliminating all truly indeterminate features, and…

2. the impossibility of enumerating the equally probable alternatives involved

Knight’s hedged account of risk obliquely acknowledges the gray area that lies between risk and uncertainty — a gray area that can be enlarged in favor of risk as our knowledge improves, or which can be enlarged in favor of uncertainty as additional complicating favors enter into our calculation of risk and render our knowledge less effective and our uncertainty all the greater. That is to say, the line between risk and uncertainty is unclear, and it can move, which makes it doubly ambiguous.

These hedges are important qualifications to make, because we all know from real-life experience that additional complicating factors always enter into actual risks. We may try to insure ourselves, and therefore to secure our interests against risk, but fine print in the insurance contract may deny us a settlement, or we may have forgotten to pay our premiums, or a thousand other things might go wrong between our careful planning and the actual events of life that so often preempt our planning and force us to deal with the unexpected with insufficient preparation. As Bobby Burns put it, “The best laid schemes o’ Mice an’ Men, Gang aft agley, An’ lea’e us nought but grief an’ pain, For promis’d joy!”

Such consideration span the entire universe from field mice to galaxies. A coldly rational assessment of risk can be made, and resources can be expended to mitigate risk to the extent calculated, but not only are the limits to our knowledge, but we don’t know where the limits to our knowledge lie. Indeterminate features can creep into our calculation and equally probable alternatives could be in play without our even being aware of the fact.

Some events that pose existential risks or global catastrophic risks can be predicted with a high degree of accuracy, and some cannot. Even about those risks that seem predictable to a high degree of accuracy — say, the life of the sun, which can be predicted on the basis of our knowledge of cosmology, and which thereby would seem to give us some knowledge of how long a time we have on earth to lay our schemes — admit of indeterminate elements and equally probably scenarios. The end of the earth seems a long way off, if the earth lasts almost as long as the sun, and putting our existential risk far in the future seems to diminish the threat.

There is a famous quote from Frank Ramsey (who died tragically young in a mountain climbing accident, as might happen to anyone, anytime) that is relevant here, both economically and philosophically:

My picture of the world is drawn in perspective and not like a model to scale. The foreground is occupied by human beings and the stars are all as small as three-penny bits. I don’t really believe in astronomy, except as a complicated description of part of the course of human and possibly animal sensation. I apply my perspective not merely to space but also to time. In time the world will cool and everything will die; but that is a long time off still and its present value at compound discount is almost nothing.

From a paper read to the Apostles, a Cambridge discussion society (1925). In ‘The Foundations of Mathematics’ (1925), collected in Frank Plumpton Ramsey and D. H. Mellor (ed.), Philosophical Papers (1990), Epilogue, 249

Despite Ramsey having referred (in another context) to the “Bolshevik menace” of Brouwer and Weyl, it has been said that Ramsey became a constructivist not long before he died. This conversion should not surprise us, given Ramsey’s Protagorean profession in his passage.

Protagoras famously said that Man is the measure of all things, of those things that are, that they are, and of those things that are not, that they are not. (πάντων χρημάτων μέτρον ἐστὶν ἄνθρωπος, τῶν μὲν ὄντων ὡς ἔστιν, τῶν δὲ οὐκ ὄντων ὡς οὐκ ἔστιν.) Protagoras may be counted as the earliest of proto-constructivists, of which company Kant and Poincaré may be considered the most famous.

In the passage quoted above, Ramsey is essentially saying in a modern idiom that man is the measure of all things, even of time and space — that man is the measure of the farthest reaches of time and space, and in so far as these distant prospects of human experience are inaccessible, they are irrelevant. Ramsey is important in his respect because of his consciously chosen anthropocentrism. In a post-Copernican age, this is significant. We are all, of course, familiar with the advocates of the anthropic cosmological principle, and their implicit anthropocentrism, but Ramsey gives us a slightly different perspective on anthropocentrism. Ramsey essentially brings constructivism to our moral life, and in so doing suggests that the moral imperatives posed by existential risk can be safely ignored for the time being.

What Ramsey is saying here is that we can make a definite calculation of the lives of the stars — and also the expected life of our sun — and that we can insure against this risk, but that the risk lies so far in the future that its present value is practically nil. In other words, the eventual burning out of the sun is a risk and not an uncertainty. On the contrary, it is not an uncertainty at all, but a certainty. Just as the finite amount of oil on Earth must eventually come to an end, the finite sun must also come to an end.

What our growing knowledge of cosmology is teaching us is that we are not isolated from the wider universe. Events on a cosmic scale have influenced the development of life on earth, and may well be responsible for our development as a species. If the earth had not been hit by an asteroid or comet about 65 million years ago, mammals may never have developed as they did, and we would not exist. And if our solar system did not bob up and down through the galactic plane of the Milky Way, resulting in geophysical rhythms from the the gravitational interaction with the rest of the galaxy, a distant asteroid of comet might not have been dislodged from its stable orbit and sent careening toward earth.

Given our connection with the wider universe, and our vulnerability to its convulsions, what we know about our local risks (which is not nearly enough, as recent unpredicted episodes have shown us) is not enough to make a calculation of our vulnerability. What appears superficially to be a calculable risk has uncertainty injected back into it by the cosmological context in which all astronomical events take place.

If the death of the sun were the only existential risk against which we needed to insure ourselves, we would not need to be in any hurry about existential risk mitigation, because we would have literally millions of years to build a spacefaring civilization and thus to insure ourselves against that predictable catastrophe. But in our violent universe (as Nigel Calder called it) scarcely a million years goes by without some cosmic catastrophe occurring, and we don’t know when then next one will arrive.

Carl Sagan rightly pointed out that an event that is unlikely to happen in a hundred years may be inevitable in a hundred millions years:

The Earth is a lovely and more or less placid place. Things change, but slowly. We can lead a full life and never personally encounter a natural disaster more violent than a storm. And so we become complacent, relaxed, unconcerned. But in the history of Nature, the record is clear. Worlds have been devastated. Even we humans have achieved the dubious technical distinction of being able to make our own disasters, both intentional and inadvertent. On the landscapes of other planets where the records of the past have been preserved, there is abundant evidence of major catastrophes. It is all a matter of time scale. An event that would be unthinkable in a hundred years may be inevitable in a hundred million.

Carl Sagan, Cosmos, Chapter IV, “Heaven and Hell”

Perhaps in one of his most quoted lines, Sagan said that we are “star stuff,” and certainly this is true. However, the corollary of this inspiring thought is that our star stuff is subject to the natural forces that shape the destinies of stars, and in shaping the destiny of stars, shape the destiny of men who live on planets orbiting stars.

Understanding ourselves as “star stuff” entails understanding ourselves as living in a dangerous universe replete with devouring black holes, gamma ray bursts, supernovae, and other cataclysms almost beyond the capacity of human beings to conceive.

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