Back in 2000 I devoted a paper to some implications of the “many worlds” interpretation of quantum mechanics proposed in 1957 by Hugh Everett III in his Princeton thesis entitled “‘Relative State’ Formulation of Quantum Mechanics”. At the time I had no notion of anybody else in philosophy interested in these issues. The article was published in French in one of the publications of the Collège International de Philosophie in Paris (“Pourquoi nous avons neuf vies comme les chats”, in Papiers du Collège International de Philosophie, Nº 51, Reconstitutions, 2000: 69-80).
Recently I discovered a series of papers by David Papineau on the subject. I reminded David that we both attended Mary Hesse’s seminar in the history and philosophy of science in Cambridge (U.K.) in the late 1970s and early 1980s. I wanted to show David my 2000 paper and we agreed in our e-mail correspondence that the best approach would be that I translate my paper in the language wherein the current debate on the subject is taking place, i.e. in English.
So here it is a couple of weeks later. I have translated the paper literally (with added inter-titles), with one exception: I’ve skipped one paragraph at the end devoted to the existence of timeless worlds, realizing when reading again the paper seven years later that what I was saying there only made sense within the alternative and classical “Copenhagen interpretation” of quantum mechanics as the argument relies implicitly on the collapse of the wave-function. Those who would still want to see the missing paragraph can turn to the original French version of the paper on my website (click here). Have fun!
Why, like cats, we have nine lives
(2007 translation of the original paper in French: « Pourquoi nous avons neuf vies comme les chats », in Papiers du Collège International de Philosophie, Nº 51, Reconstitutions, 2000: 69-80)
Armel and I had stopped on the western side of rue de Condé in Paris. Francis who was aware that we were on our way to take the metro at Odéon has also stopped. However, Isabelle who was unaware of our plans had already crossed the street. She suddenly realizes that she’s the only one to have done so and comes back briskly on her tracks. But a car driven at full speed irrupts that will not manage to avoid hitting her…
A few seconds later I hear myself say to her: “I did see your blood covering the road.” Armel says: “The car passed only inches from you.”
I wake up right in the middle of the night and I think: “I truly saw her lying dead: I did see Isabelle’s blood on the road. Soon afterwards I saw her alive but for a fraction of a second I did not imagine her being dead: I literally saw her dead.” I say to myself: the world bifurcated, I was at one point part of a world where Isabelle died and soon afterwards part of a world where – thank God! – she was alive. Didn’t that fleeting vision of the accident imply a brief coexistence of two incompatible state-of-things? A co-existence which – as it is assumed by quantum mechanics – gets resolved by the sudden synthesis of two equally possible state-of-affairs until then superimposed (the famous “collapse of the wave-function”).
I start thinking of what report survivors of a “near-death experience” who claim having experienced that their consciousness (soul) is “hovering” above the scene where their body struggles between life and death. They mention that such contemplation was brutally interrupted and that they regained consciousness, that is, that their consciousness was all of a sudden reunited with their bruised body in a process reminiscent of the collapse of the wave-function at the quantum level.
I go back to sleep. A little later, still in the middle of the night, I wake up once again and within a couple of minutes a series of philosophical consequences of the “many worlds” hypothesis precipitate in my reflection: a deductive stream comprising the reconciliation of the standpoints of realism and of idealism; a confirmation of the Leibnizian concept of the “best of all possible worlds”; an expansion of the Cartesian cogito; the role played by Reason in History; ; finally, how to conceive (in a non-contradictory way) the essence of Being.
Does consistency entail truth?
It goes without saying that when I woke up in the morning, I’d stopped believing in any of those tall stories and I assigned their conception to the relaxation of the critical faculties characterizing nocturnal ponderings. Still… during the day I went back several times to these reflections, still astonished at the aesthetic beauty of an approach which answers some classical philosophical questions, all starting from the “many worlds” hypothesis. It is this sentiment of the beauty of the deductive waterfall which encourages me to write it down, in spite of what I regard as its quasi null plausibility .
What struck me during my nocturnal reflection was not only the ease with which those questions coming to my mind were solved but even more so how these – seeming to me until then disparate – were organizing themselves harmoniously as a whole, precisely because a solution was given to them in a deductive order. We got used to the idea that science is the domain of questions which would end up being solved while philosophy, in reverse, that of those which would remain open. But – rightly or wrongly – science has disappointed us in that regard. Does the reversal of perspectives apply also to philosophy, meaning by that that its own questions can also get solved?
But how could we trust a world representation the sole merit of which is to help solve an important set of questions having occupied over the ages the attention of philosophers? In other words, what guarantee does a theory provide as to its truth if its single virtue is its consistency, its very capacity at being systematic? Would such a disposition to answer these questions without self-contradiction offer it – inductively speaking – a truthfulness which otherwise – with regard to its contents – would be flatly denied to it?
Snow’s “two cultures”
An intellectual debate has recently taken place the object of which was the contention that philosophers most often misunderstand the meaning of views held by scientists. The alleged reason was that the epistemological scope of the scientific theories and of the facts from which philosophers build an argument is in truth beyond their reach, in such way that, contrary to what they assume, philosophers do not build upon the scientific experience but find there nothing more than a “source of inspiration” (cf. Sokal & Bricmont 1997; Bouveresse 1999). I’m offered here an opportunity to respond indirectly to that accusation when demonstrating what occurs when a philosopher takes in earnest what scientists hold as true, in this instance with the implications of the so-called “many worlds” theory which assumes that the universe keeps splitting into a multitude of parallel worlds . The outcome of my reflection, presented in two stages is, as will be seen, surprising at every step of its development.
Everett’s “many worlds” interpretation
Lay persons are sometimes introduced to the unexpected behavior at the microscopic level of elementary particles studied by quantum mechanics through the thought experiment of “Schrödinger’s cat” leading to the “many worlds” hypothesis. The premise is that of competing states of reality remaining superposed until some event such as their observation – or rather the interaction with them which their measurement supposes – forces them to choose a manner to be, and this, paradoxically, without any of the alternatives implicit within the initial superposition losing their reality, i.e. occurring also in their own right . The interaction – of which measurement is but one of the possible forms – is then the motive for the bifurcation of worlds between two of their potential modes.
In the thought experiment devised by Schrödinger in the 1930s, a cat whose survival hangs on the breaking or not of a vial containing cyanide finds himself simultaneously dead and alive in two equi-possible but bifurcating worlds: two worlds having diverged from each other. Whether the vial breaks or not is determined by a quantum fluctuation with a fifty percent chance of occurrence. In the classical “Copenhagen” interpretation of quantum mechanics the wave-function collapses and the world “chooses” between the two equally possible outcomes. In the “many worlds” interpretation, the cat is simultaneously dead and alive in two words in the process of splitting (“decohering”) , the ontology underlying this conception being thus that of a myriad of co-existing worlds, each of them evolving following a script proper to it, hence the “many worlds” appellation for this particular interpretation of quantum mechanics.
Life and death in “many worlds”
What – to my knowledge – has never been debated in the discussions around Schrödinger’s cat is the way he sees it himself, possibly because the author of the thought experiment assumed that the animal is not fully aware of what is happening to him. Let’s replace therefore the cat by a human being so to make the experiment more telling. If the latter is both dead and alive one is free to assume that the common principles applying to consciousness remain valid in both cases, meaning by that that 1o in that world where he is dead, his corpse is devoid of consciousness while 2º in that world where he is still alive, his body remains conscious, i.e. experiences to be alive (unless he is asleep or in a coma). In other words, in a case where two scripts diverge where in one the person dies and in the other that person remains alive, self-awareness remains automatically attached to that script where the body’s metabolic functions remain unimpaired .
According to some prominent contemporary physicists, the existence of such bifurcations between possible worlds has been established beyond any reasonable doubt. I intend now to draw from this some consequences. The first is the following : should there exist competing strategies where the unsuccessful alternative implies the death of the subject choosing it, he will fail to notice it as his self-awareness remains necessarily attached to that (or those) many worlds where he stays alive – however low the probability of the script to which this (or these) correspond. He will therefore fail to notice that his choice of a strategy was infelicitous. Within the autobiographic narrations which he will be happy to share in the world where he survives, he will go so far as justifying to whomever is prepared to lend him a listening ear the alleged wisdom of his poor judgment, involuntarily reinforcing that way his inclination towards calamitous tactical moves. Such a strategy will last until he encounters circumstances when his probability of survival has become objectively nil. We’re all familiar with characters utterly proud of their prowess to whom we assign no talent whatsoever for what positive becomes to them but only the inordinate quality of their luck.
This phenomenon would account for an observation made by psychologists about the irrational behavior of compulsive gamblers (Tversky & Wakker 1995) displaying an attitude which other animals aren’t burdened with: entrenchment in error. The type of self-reflection characterized by unwarranted self-congratulation (“my choice was so judicious…”) about decisions bound to materialize in ineluctable death in a parallel world, is necessary for such entrenchment in error to develop evolutionarily. Indeed, the animal being deprived of consciousness is faced with the objectivity of the success or failure of its behavior while man, whose consciousness remains out of necessity linked to that world where his body stays alive, is encouraged to persevere in his self-defeating tactics, however inept he has shown himself in the task of ensuring his own survival.
Since I’ve just mentioned gambling I feel entitled to propose the following theorem in a “many worlds” perspective: Russian roulette is a riskless pursuit with a significant potential for profit (this applies also to any type of extreme sports). This is truly a simple corollary of what I just suggested: the player saves his skin – at least within his own story: that whereto his self-awareness is attached – as long as there is within the range of possible scripts at least one where he manages to stay alive. As in Russian roulette the chance of surviving is set – per definition – at five out of six, the player escapes unscathed every time. Of course, as far as others around him are concerned he dies necessarily one time out of six, but as far as he’s concerned, the risk of dying due to playing the game is nil. Surely he’s bound to die one day for some other reason: whenever his probability of survival within the whole set of possible scripts open to him has lowered to zero. This means that in most cases he’ll end up dying “subjectively” from a natural death due to the ultimate corruption of his material body. The long-lasting existence of the game over the centuries, in spite of its seeming danger derives from the theorem’s truth.
I just mentioned that in the surroundings of a Russian roulette player, his partners die one time out of six while as far as he is concerned that probability is nil. More generally, all actors succumbing to a violent death in the story I personally experience do lead in fact a much more peaceful life within their own story (by which I mean the subjective experience they have of it). Conversely, the adventurous life that I’m leading appears much more dangerous to my contemporaries than to myself, my own capacity at escaping unscathed from the most compromised circumstances being, as we’ve seen, considerable. This last observation may be generalized in a second theorem: Each of us leads (subjectively) a much more peaceful life than what his contemporaries observe.
The story of one’s own consciousness follows thus necessarily an “optimistic” slant meaning that, on the whole, one will get away with things, if not forever, at least a significant number of times . The classical notion of providence refers to this principle that we all observe busily at work within our own lives. This explains in particular why a large proportion of desperate situations still find a happy ending deemed “providential” and this despite the objectively low probability of such unexpected “reversals of fortune.” For instance, despite the objective ineluctability of a thermo-nuclear world war – due to a basic cultural misunderstanding between the over-armed protagonists, both inclined to paranoid reasoning – we, likely readers of my text, have all survived World War III. A set of questions which go without saying for any individual within Western culture, like “Why me here and now… what is the meaning of the world surrounding me relative to my own existence?” etc. find then each a nearly self-evident response while, together, they lock in into an aesthetically satisfactory whole.
The meaning of life
My own consciousness arises out of necessity within the single world where my existence is possible. Because it is, among the multitude of worlds in existence, the only one where my own existence is able to manifest itself, within this singular world my existence is not contingent but necessary: this singular world and my own existence in its midst are consubstantial. As it is necessary to it, my presence within the world I inhabit is ontologically speaking unproblematic. The obviousness of this thesis would show plainly if it were given to me to observe simultaneously my presence here and now within the sole world that I live in and my total absence from the myriads of alternative parallel worlds where my existence is impossible. That type of experience is of course beyond our reach as the observation by me of another singular world than that I live in would imply my necessary presence in it, which is contradictory.
My own necessity within a singular world is accompanied by that of all events preceding my coming into its history. These do not take their meaning from the sole fact of my own existence: they are meaningful just as well because of the existence of six billons of my contemporaries . This being said, it would be irrelevant for me to wonder about seeming oddities – due to their unlikelihood – in their sequence: it is their particular configuration which made me possible; any alternative resulted in ontologically distinct worlds: even if the events which presided to the existence of those worlds were much more “plausible” my existence there would remain impossible.
The best of all possible worlds
The ontological price to pay for the parallel existence of myriads of contingent worlds is the necessity per se of each of them, meaning the intrinsic necessity of every event taking place in it within its own sequence – in other words what is deemed as “determinism.” Let’s illustrate this with an unlikely series of events: my mother survives World War II due to the following circumstances. Her own mother, a non-Jew – dies in 1941 in occupied Belgium from a rapidly evolving cancer. My grandfather – Jewish – finds himself with the status of family head having under his responsibility non-Jewish children and for that reason closely escapes deportation.
I’ve often thought of Nazism’s uncanny rationality which – taking literally the Jewish genealogical logic – authorized my grandfather’s survival while his brothers and sisters vanished in death camps. Within a “many worlds” approach my wondering is however uncalled for: my own existence supposes automatically that within my own world Nazis adopted a matrilinear logic to rule the way they processed Jews. This doesn’t mean that my existence explains or justifies their approach; it simply means that the only possible world where my existence manifests itself is one where Nazis applied to the extermination of Jews a matrilinear logic: in that or in all those where – in a perspective a lowered rationality – they adopted a patrilinear logic, I simply failed to be born. Other example, for 200,000 years Neanderthals were contemporaries of Homo Sapiens. Why did they then vanish? The question in truth is idle through logical necessity. Indeed, in a parallel world, a conscious subject notices being a Neanderthal and asks himself a question symmetrical to mine: what did possibly happen with Homo Sapiens?
There is no need therefore for me to worry about the conditions for my own existence: they are a necessary given of my idiosyncratic world. And this, not because my own existence would give that world its meaning but because within this idiosyncratic world there exists a double necessity: of its evolution as it took place and of my presence within it at a particular period in time. In other words, my existence imposes a retrospective constraint on the world where I show up: my existence is contingent within the context of all possible worlds but it is indispensable within the singular world whereof I’m talking and wherefrom I’m talking.
From my own standpoint this implies I necessarily live in that of the many worlds where I automatically find my bearings as not only are all events that took place there before I was born compatible with it but also because as long as I stay alive all contemporary events are similarly compossible with me. For all of us – the complete “cohort” of contemporaries – our existence imposes a set of identical constraints on the past existence of the world; the same applies of course always and everywhere for every cohort. This establishes between the members of any cohort a Leibnizian “compossibility”: whatever the apparent variety of my contemporaries, we are linked together by the fact that our simultaneous emergence to existence is “compossible,” compatible with the antecedent history of a singular world. The same works symmetrically with the future.
The world we offer our descendants is the same as our own until the time when they are conceived. Later, each of these worlds begins to split. Consequently it is not entirely vacuous wishing generously to entrust one’s own children a better world: theirs is out of necessity identical to ours over some part of its history as being submitted to the same set of constraints which its prior history entails: my own children’s world can only start bifurcating once I’ve lived in it for a certain time .
The end of my compossibility with my world amounts to my death. In old age my metabolism exhausts itself in attempting to maintain the compossibility of my cells and of my organs with the world I belong. As long as there remains one such world where my existence is possible, my consciousness remains attached to it. This allows me to constantly stick to what is for me the best of all possible worlds, that where – often against all plausibility – I’m staying alive. What has been rediscovered here is naturally a well-known Leibnizian thesis; it has been rediscovered though ironically. Each of us lives in the best possible world with the crucial qualification that there is no single world bearing that property. For each of us our world is only the best possible world because, on the one hand, such worlds exist in the background in astronomical collections (due to their incessant disposition to diverge from each other and follow distinct tracks) and, on the other hand, because our consciousness – being attached to our material body – holds automatically the providential ability to stick to that that punishes us in the most benign manner for our mistakes. Besides, this harmony does not result as with Leibniz from a divine will external to our world but from the ontological haziness characterizing nature at the quantum level’ [Hegel claims that with Leibniz this divine will is “as it were, the waste channel into which all contradictions flow” ( 1995: 348).
Cogito ergo sum
From this follows a conception providing a reconciliation of idealism and realism. The world exists indeed but the one I’m given to observe is necessarily “my world”: it is its constraints which justify my emergence into existence. It is no doubt not my own existence which provides to this world its full meaning but it does contribute to tits meaning: this world is fully mine and I share it with the cohort of my contemporaries even if their paths within that world diverge continuously from mine. Hence a possible extension of the Cartesian cogito: “I think therefore I am: I am therefore my world is in a certain way.” The fact of my consciousness allows me to apprehend the world where I exist while that existence of mine is consubstantial with a singular world; this means that there exists on that world a constraint which is that of my compossibility with all else composing that world. The very fact that I think does not shape that world, nor does it determine it post hoc but I and the world where my consciousness dwells are inseparably tied within the fabric of a unique script among the myriads of others which are not only possible but do actually materialize themselves independently.
Reason in History
In the same way, my existence and the consciousness I hold of it, appearing after a considerable number of generations have succeeded each other, entail that over that very long period collaborative behavior between human beings has reproduced itself consistently. The further I show up in human history, the more my own existence entails – as a constraint – the ability of the human species to survive over a longer period; the probability of such an uninterrupted sequence depends on the reduction of the self-destructive tendencies that my species has displayed over history and on the emergence, conversely, of increasingly collaborative traits. In other words, the further I intervene in my world’s history, the more my existence entails progress in my species’ reconciliation with itself. What is observed here is not the manifestation of an evolutionary principle at work but the implications of a rational constraint. This means that the further I appear within my world’s history, the more my existence entails the manifestation of reason in the history of that world. But also, and whichever the time when a consciousness becomes aware of itself, that consciousness will necessarily observe in the period that preceded its advent the manifestation of reason in history. More specifically, my existence does not prevent Nazi barbarity in the years which immediately precede my own birth but it supposes the limited rationality which makes them adopt the Judaic notion of genealogy when they undertake to exterminate Jews. Each of us belongs fully to the time where he or she was born. It is no accident that I get born in 1946, it is indeed in that year that the space of my possibility opens up: neither before, nor after but at that very moment within a singular world.
We all receive therefore our own time as an inalienable gift: that time is not only the time where each of us has become possible but also that time where his or her absence would leave its mark as a genuine void. I carry in my own essence the imprint of the barbarity that preceded shortly my birth, as well as of that surrounding me since. In other words, it is not foreign to me: I partake to the world where it resides. There is consubstantiality, automatic harmony between my time and myself; I am the fruit of it while my time bears carved in it my imprint: in no way could I not have belonged to my time.
The anthropic cosmological principle
Some years back, John Barrow and Frank Tipler (1986) proposed their “anthropic cosmological principle.” Starting from the observation that a world likely to generate creatures similar to ourselves is out of necessity very specifically constrained within a narrow range of possible values for universal physical constants, Barrow and Tipler regard such a configuration as highly unlikely and our universe therefore resulting from a design. The startling nature of such a coincidence fades away however if it is established that besides that world exist also myriads of parallel worlds where these constants hold different values. The supposedly “significant” observation of the very low probability of an “anthropic” universe turns out to be trivial in the “many worlds” perspective. Under its trivialized form, the “anthropic cosmological principle” can be reformulated in the following way: We necessarily appear in a world where our existence is possible and are necessarily absent from worlds where it is impossible.
Consequently, it is most unlikely that exist other inhabited stellar systems in any world where I’m myself present: the chain of events necessary to lead to the rise of consciousness under the guise which I observe in myself and in my fellow humans is much too singular to imagine that anywhere else in that same world it has arisen under an analogous shape. In that respect, Barrow and Tipler are no doubt right: the meaning of our world resides in some way in ourselves and, within every possible world where consciousness has arisen it is the form under which it manifests itself that provides it with a meaning, in the way that, as Schelling conceived it, Man, or under its generalized form, Reason, is the means by which Nature becomes aware of itself (Schelling as quoted by Hegel  1995: 517).
Time has come now to undo the scaffolding which constituted in my paper the many worlds hypothesis and examine what would ensue. What I mean to elicit is whether the answers I offered to some classical philosophical questions would still stand if physicists subscribing to the “many worlds” view were wrong and if the spontaneous interpretation we hold of the world, i.e. that there is in truth only one, were actually correct. If so, what would then appear is that the kind of questions philosophy asks does constitute a system and this prior to the fact that one can – as I did here – link them in a deductive mode. In other words, when asking over the ages the same questions I asked here, philosophy was in fact entailing a very specific ontology, half-realist, half-idealist, comprehending both a modeled representation of that world and what comes closest to what a human being may consider as its meaning per se and relative to him or her, i.e. a full-fledged and comprehensive notion of Being.
What is more, the reason why the simple fact of asking such questions equates with love of wisdom has become obvious. Our necessary presence within a world entirely made of compossible existences offers the terms of a reconciliation: how to work at maximizing compossibility through extending the compatibility and complementarity of consciences. This world accompanied by the horror specific to the time we are born (I’m speaking here to the members of my cohort) is undoubtedly ours in a non–contingent manner. If we don’t like it we should feel free to change it to our whims. When doing so we need to remain aware that we are only modifying a singular world among myriads of parallel worlds. Still it remains that we are free to modify one . And to do so we possess as an invaluable asset that – like cats – we are given the chance to be deadly wrong about how to proceed, eight times.
1 Removed 2007: “what one should think of the notion that time has only a purely psychological reality”.
2 I’ve changed my mind on this (2007).
3 The “many worlds” theory is a reformulation of quantum mechanics published in 1957 by Hugh Everett III in the thesis he defended at Princeton. Other famed physicists such as Gell-Mann and Hartle, subscribe to close varieties of that interpretation. Price remarks that “[Many-worlds is a return to the classical, pre-quantum view of the universe in which all the mathematical entities of a physical theory are real” (Price 1994-95).
4 Price: “According to many-worlds all the possible outcomes of a quantum interaction are realized. The wave-function, instead of collapsing at the moment of observation, carries on evolving in a deterministic fashion, embracing all possibilities embedded within it. All outcomes exist simultaneously but do not interfere further with each other, each world having split into mutually unobservable but equally real worlds” (Price 1994-95).
5 Price: “From the surviving cat’s point of view it occupies a different world from its unlucky and late copy” (Price 1994-95).
6 Death in one of the scripts leads to a quick divergence between the two worlds: “The worlds split or ‘decohere’ from each other when irreversible events occur. [… Those] irreversible processes, in particular, will destroy almost any possibility of interference effects being restored in the future [between the worlds having diverged]” (Price 1994-95). In reverse, in the absence of such irreversibility, the full set of worlds where I stay alive quickly restore their unity. Evoking the fact that we don’t experience (within the world where we remain alive) the effect of such bifurcations, Price observes: “Arguments that the world picture presented by this theory is contradicted by experience, because we are unaware of any branching process, are like the criticism of the Copernican theory that the mobility of the earth as a real physical fact is incompatible with the common sense interpretation of nature because we feel no such motion. In both case the arguments fails when it is shown that the theory itself predicts that our experience will be what it in fact is. (In the Copernican case the addition of Newtonian physics was required to be able to show that the earth’s inhabitants would be unaware of any motion of the earth.)” (Price 1994-95).
7 A number of times that intuition – founded on empirical evidence – has evaluated as nine, before this disposition to relative immortality got assigned to cats, hence the title of my essay.
8 Excluding here all other living creatures and all inert entities – which are being ignored due to the very special quality of self–reflection authorized by consciousness. Animals – or some of them – might also experience consciousness but, by contrast with my fellow humans, they fail (in any case with most of us) at convincing us that they do (Schrödinger’s cat in particular).
9 Price : “[the notion of] many-histories defines a multiply-connected hierarchy of classical histories where each classical history is a “child” of any parent history which has only a subset of the child defining irreversible events and a parent of any history which has a superset of such events” (Price 1994-95).
10 One paragraph removed.
11 Unless the feeling of freedom accompanying consciousness is purely illusory. I need to mention this as I defended that thesis elsewhere (Jorion 1999). If, as I claimed in that earlier essay consciousness is deprived of any decisional power we are then reduced to being powerless witnesses of our own history, able at most to generate about it an autobiographical narrative ratifying the facts post hoc. Consciousness as a dead-end-street is a possible interpretation for the Platonic myth of the cave (see also Griswold 1999: 14).
Barrow, John D. & Tipler, Frank J., The Anthropic Cosmological Principle, Oxford: Oxford University Press, 1986
Bouveresse, Jacques, Prodiges et vertiges de l’analogie, De l’abus des belles-lettres dans la pensée, Paris: Éditions Raison d’Agir, 1999
Griswold, Charles S. Adam Smith and the Virtues of Enlightenment, Cambridge: Cambridge University Press, 1999
Hegel, G. W. F., Lectures on the History of Philosophy, III,  Lincoln: University of Nebraska Press, 1995
Jorion, Paul, Le secret de la chambre chinoise, L’Homme, 150: 177-202, 1999
Price, Michael, Frequently Asked Questions about Many-Worlds, http://www.geocities.com/Athens/Acropolis/1756/everett.txt
Sokal, Alan & Bricmont, Jean, Impostures intellectuelles, Paris: Odile Jacob, 1997
Tversky, Amos & Wakker, Peter, Risk Attitudes and Decision Weights, Econometrica, 1995, vol. 63, i, 6: 1255-1280