Of Clouds and Clocks Part 1

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6. Of Clouds and ClocksAN APPROACH TO THE PROBLEM OF RATIONALITYAND THE FREEDOM OF MAN

MY predecessor who in this hall gave the first Arthur HollyCompton Memorial Lecture a year ago was more fortunate than1. He knew Arthur Compton personally; I never met him.,But I have known of Compton since my student days in thenineteen-twenties, and especially since 1925 when the famousexperiment of Compton and Simonz refuted the beautiful butshort-lived quantum theory of Bohr, Kramers, and Slater.3 Thisrefutation was one of the decisive events in the history of quan-tum theory, for from the crisis which it created there emergedthe so-called new quantum theory'-the theories of Born andHeisenberg, of Schrodinger, and of Dirac.

It was the second time that Compton's experimental tests hadplayed a crucial role in the history of quantum theory. The firsttime had been, of course, the discovery of the Compton effect,the first independent test (as Compton himself pointed out4) ofEinstein's theory of light quanta or photons.Years later, during the Second World War, I found to mysurprise and pleasure that Compton was not only a greatphysicist but also a genuine and courageous philosopher; andfurther, that his philosophical interests and aims coincided with

When I came to Berkeley early in Feb. 1962 I was eagerly looking forwardto meeting Compton. He died before we could meet.2 A. H. Compton and A. W. Simon, Phys. Rev. 25, 1925, pp. 309 if. (See also W.

Bothe and H. Geiger, Zeit. f. Phys. 26, 1924, PP. 44 ff., and 32, 1925, pp. 639 ff.;Naturwissenschaften, 3, 1925, P 440) N. Bohr, H. A. Kramers, and J. C. Slater, Phil. Mag. 47 1924, pp. 785 if., and,Zeitschr. f. Phys., 24 1824, pp. 69 if. See also A. H. Compton and S. K. Allison,X-R ay s i n The or y an d E xpe r i m e n t 1935; for example, pp. 211-27.4 See chapter I, section 19, of Compton and Allison (note 3).

This was the second Arthur Holly Compton Memorial Lecture, presented atWashington University on 2 1 Apr. 1965.

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my own on some important points. I found this when, almostby accident, I got hold of Compton's fascinating Terry Lectureswhich he had published in 1935 in a book entitled The Freedomof Man.5You will have noticed that I have incorporated the title ofCompton's book, The Freedom of Man into my own title today.I have done so in order to stress the fact that my lecture will beclosely connected with this book of Compton's. More precisely,I intend to discuss the same problems which Compton discussedin the first two chapters of this book, and again in the secondchapter of another of his books, The Human Meaning of Science.6In order to avoid misunderstandings I must stress, however,that my lecture today is not mainly about Compton's books. Itis rather an attempt to look afresh at the same ancient philo-sophical problems with which he grappled in these two books,and an attempt to find a new solution to these ancient prob-lems. The sketchy and, very tentative solution I am going tooutline here seems to me to fit in well with Compton's mainaims, and I hope- indeed I believe-that he would haveapproved of it.

THE central purpose of my lecture is to try to put these ancientproblems simply and forcefully before you. But first I must saysomething about the clouds and clocks which appear in the titleof my lecture.My clouds are intended to represent physical systems which,like gases, are highly irregular, disorderly, and more or lessunpredictable. I shall assume that we have before us a schemaor arrangement in which a very disturbed or disorderly cloudis placed on the left. On the other extreme of our arrangement,on its right, we may place a very reliable pendulum clock, aprecision clock, intended to represent physical systems whichare regular, orderly, and highly predictable in their behaviour.

A. H. Compton, The Freedom of Man, 1935 (third edn., 1939 . This book wasbased mainly on the Terry Foundation Lectures, delivered by Compton at Yalein 1931, and in addition on two other series of lectures given soon after the TerryLectures.

6 A. H. Compton, T h e H u m a n Meaning of Science 1940.


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2o 8f Clouds and ClocksAccording to what I may call the commonsense view ofthings, some natural phenomena, such as the weather, or thecoming and going of clouds, are hard to predict: we speak of the`vagaries of the weather . On the other hand, we speak of clock-work precision' if we wish to describe a highly regular andpredictable phenomenon.There are lots of things, natural processes and natural pheno-mena, which we may place between these two extremes-theclouds on the left, and the clocks on the right. The changingseasons are somewhat unreliable clocks, and may therefore beput somewhere towards the right, though not too far. I supposewe shall easily agree to put animals not too far from the cloudson the left, and plants somewhat nearer to the clocks. Amongthe animals, a young puppy will have to be placed further to theleft than an old dog. Motor cars, too, will find their place some-where in our arrangement, according to their reliability: aCadillac, I suppose, is pretty far over to the right, and evenmore so a Rolls-Royce, which will be quite close to the best ofthe clocks. Perhaps furthest to the right should be placed thesolar syst em.?As a typical and interesting example of a cloud I shall makesome use here of a cloud or cluster of small flies or gnats. Likethe individual molecules in a gas, the individual gnats whichtogether form a cluster of gnats move in an . astonishinglyirregular way. It is almost impossible to follow the flight of anyone individual gnat, even though each of them may be quitebig enough to be clearly visible.Apart from the fact that the velocities of the gnats do notshow a very wide spread, the gnats present us with an excellentpicture of the irregular movement of molecules in a gas cloud,or of the minute drops of water in a storm cloud. There are,of course, differences. The cluster does not dissolve or diffuse,but it keeps together fairly well. This is surprising, consideringthe disorderly character of the movement of the various gnats;but it has its analogue in a sufficiently big gas cloud (such as ouratmosphere, or the sun) which is kept together by gravitationalforces. In the case of the gnats, their keeping together can beeasily explained if we assume that, although they fly quiteirregularly in all directions, those that find that they are getting

7 For the imperfections of the solar system see notes i i and 16 below.

6. Of Clouds and Clocks09away from the crowd turn back towards that part which isdensest.This assumption explains how the cluster keeps together eventhough it has no leader, and no structure-only a randomstatistical distribution resulting from the fact that each gnatdoes exactly what he likes, in a lawless or^ random manner,together with the fact that he does not like to stray too far fromhis comrades.I think that a philosophical gnat might claim that the gnat.society is a great society or at least a good society, since it is themost egalitarian, free, and democratic society imaginable.

However, as the author of a book on The Open Society I woulddeny that the gnat society is an open society. For I take it to beone of the characteristics of an open society that it cherishes,apart from a democratic form of government, the freedom ofassociation, and that it protects and even encourages the forma-tion of free sub-societies, each holding different opinions andbeliefs. But every reasonable gnat would have to admit that inhis society this kind of pluralism is lacking.

I do not intend, however, to discuss today any of the social

or political issues connected with the problem of freedom; andI intend to use the cluster of gnats not as an example of a socialsystem, but rather as my main illustration of a cloud-likephysicalsystem, as an example or paradigm of a highly irregular ordisordered cloud.Like many physical, biological, and social systems, the clusterof gnats may be described as a `whole'. Our conjecture that it iskept together by a kind of attraction which its densest partexerts on individual gnats straying too far from .the crowd showsthat there is even a kind of action or control which this `whole'exerts upon its elements or parts. Nevertheless, this `whole' canbe used to dispel the widespread `holistic' belief that a `whole'is always more than the mere sum of its parts. I do not denythat it may sometimes be so.8 Yet the cluster of gnats is anexample of a whole that is indeed nothing but the sum of its

8 See section 23 of my book The Poverty of Historicism (1957 and later edns.),where I criticize the `holistic' criterion of a `whole' (or `Gestalt ) by showing thatthis criterion ('a whole is more than the mere sum of its parts') is satisfied even bythe favourite holistic examples of non-wholes, such as a `mere heap' of stones.(Note that I do not deny that there exist wholes; I only object to the superficialityof most holistic' theories.)


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21 0 Of Clouds and Clocksparts-and in a veryprecisesense; fornot onlyis it completelydescribed by describing the movements ofall the individualgnats, but themovement of thewhole is, in this case,preciselyth e (v ectorial) s umof t he mov em en ts o f i ts constituen tm em bers,dividedbythe number ofthe members.Anexample(in manyways similar)of abiological systemor`w hole whichexerts somecontrol overthe highlyirregularmovementsof its parts wouldbe apicnicking family-parentswitha few children and adog-roamingthewoods for hours,but never strayingfarfromthefamily car (which acts like acentreofattraction, asit were).This system maybe said tobeeven morecloudy-that is, less regularin the movementof itsparts-thanourcloudof gnats.I hopeyou will nowhavebefore you anideaofmy two proto-typesor paradigms, theclouds on theleftandtheclocks ontheright, and of the way inwhich we canarrangemany kinds ofthings,andmanykinds ofsystems,between them. I amsure youhavecaught somevague, generalideaofthe arrangement, andyou neednot worry if yourideaisstillabit foggy, or cloudy.

THEarrangementI have described is, it seems, quite acceptableto common sense;andmore recently, inourowntime, it hasbecome acceptable evento physical science. It was not so, how-ever, duringthe preceding250years: theNewtonian revolution,oneof the greatest revolutionsin history, ledto the rejection ofthecommonsensearrangementwhich I havetriedto present toyou. For one of the thingswhich almosteverybody9thought hadbeen establishedby the Newtonianrevolution was thefollowingstaggeringproposition:

All cloudsareclocks even themost cloudy of clouds.This proposition, `All cloudsareclocks , may be takenas a

brief formulation oftheviewwhich I shall call `physical deter-minism .Thephysicaldeterminist who says that all cloudsareclockswillalsosaythat ourcommonsensearrangement, withtheclouds o n th el eft and the c locks on t heri g ht, ismis le ad ing, sinceNewton himself was not amongthose whodrewthese`deterministic con-

sequences from his theory; see notes i i and i6below.

6. OfClouds andClocks 21 1everything oughtto be placedon the extreme right. He will saythat,withall our common sense,wearranged things not accordingto their nature but merelyaccording toourignorance. Our arrange-ment,he will say, reflects merelythe fact that we know in somedetailhowtheparts ofa clock work,or howthe solarsystemworks, whilewedo not have any knowledgeabout the detailedinteraction ofthe particlesthatforma gas cloud,or an organ-ism.Andhe will assert that,oncewehaveobtainedthisknow-ledge,we shallfindthatgas clouds or organismsareas clock-likeas our solar system.

Newton stheory did not, ofcourse, tell thephysicists that thiswasso. In fact,it didnot treat atall of clouds. Ittreatedespecially of planets, whose movementsit explainedas due tosomeverysimple lawsof nature; also of cannonballs, and of thetides. But itsimmense success i n these fieldsturnedthephysi-cists heads; andsurely not without re aso n.Before thetimeof Newtonandhis predecessor, Kepler, themovements of theplanets had escaped manyattemptsto explainor eventodescribethemfully. Clearly, theysomehow partici-pated inthe unvaryinggeneral movement of the rigid system ofthe fixed stars; yettheydeviated from the movementof thatsy stem alm ost likesin gle gnat sd ev iating from th e g en eral mov e-mentof acluster of gnats. Thustheplanets, not unlike livingthings,appearedto be ina positionintermediatebetweencloudsandclocks. Yet the successof Kepler s and even moreof New-tons theoryshowed that thosethinkershad beenrightwhohadsuspected that theplanetswerein fact perfect clocks. For theirmovements turnedout to bepreciselypredictable withthe helpof Newtonstheory; predictable inallthosedetailswhich hadpreviously baffledtheastronomers by their apparent irregularity.Newto ns th eor ywas the first re allysu ccessful s cientific t heor yinhumanhistory; and it wastremendouslysuccessful. Here wasreal knowledge; knowledgebeyond the wildestdreamsof eventheboldest minds. Here was a theory which explainedpreciselynotonlythe movements of all the stars intheir course, but also,just as precisely, the movements ofbodies on earth,suchasfallingapples, orprojectiles,or pendulumclocks. And it evenexplainedthe tides.All open-mindedmen-all those who wereeager tolearn,and whotookan interest inthe growthof knowledge-were


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21 2 f Clouds and Clocksconverted to the new theory. Most openminded men, andespecially most scientists, thought that in the end it wouldexplain everything, including not only electricity and magnet-ism, but also clouds, and even living organisms. Thus physicaldeterminism-the doctrine that all clouds are clocks-becamethe ruling faith among enlightened men; and everybody whodid not embrace this new faith.was held to be an obscurantistor a reactionary.10

AMONG the few dissenters was Charles Sanders Peirce, thegreat American mathematician and physicist and, I believe, oneof the greatest philosophers of all time. He did not questionNewton s theory; yet as early as 1892 he showed that this theory,even if true, does not give us any valid reason to believe thatclouds are perfect clocks. Though in common with all otherphysicists of his time he believed that the world was a clock thatworked according to Newtonian laws, he rejected the belief thatthis clock, or any other, was perfect down to the smallest detail.He pointed out that at any rate we could not possibly claim toknow, from experience, of anything like a perfect clock, or ofanything even faintly approaching that absolute perfectionwhich physical determinism assumed. I may perhaps quote oneof Peirce's brilliant comments: `. . . one who is behind thescenes' (Peirce speaks here as an experimentalist) `... knowsthat the m ost refined com parisons [even] of masses [and] lengths,... far surpassing in precision all other. [physical] measurements,... fall behind the accuracy of bank accounts, and that the ...determinations of physical constants ... are about on a par with

The conviction that determinism forms an essential part of any rational orscientific attitude was generally accepted, even by some of the leading opponentsof `materialism' (such as Spinoza, Leibniz, Kant, and Schopenhauer). A similardogma which formed part of the rationalist tradition was that all knowledge beginswith observation and proceeds from there by induction. Cp. my remarks on thesetwo dogmas of rationalism in my book Conjectures and Ref utations, 1963, 1965,1969, 1972, PP- 122 f-

Newton himself may be counted among the few dissenters, for he regardedeven the solar system as imperfect, and consequently as likely to perish. Because ofthese views he was accused of impiety, of casting a reflection upon the wisdom ofthe author of nature' (as Henry Pemberton reports in his A V iew of Sir Isaac Newton sPhilosophy, 1728, p. 18o).

6. Of C louds and Clocks 1 3an upholsterer's measurements of carpets and curtains . . 2.12From this Peirce concluded that we were free to conjecture thatthere was a certain looseness or imperfection in all clocks, and thatthis allowed an element of chance to enter. Thus Peirce conjecturedthat the world was not only ruled by the strict Newtonian lawsbut that it was also at the same time ruled by laws of chance, orof randomness, or of disorder: by laws of statistical prob bilityThis made the world an interlocking system of clouds andclocks, so that even the best clock would, in its m olecular structure,show some degree of cloudiness. So far as I know Peirce was thefirst. post-Newtonian physicist and philosopher who thus daredto adopt the view that to some degree all clocks are clouds; or inother words, that only clouds exist, though clouds of very differentdegrees of cloudiness.Peirce supported this view by pointing out, no doubt cor-rectly, that all physical bodies, even the jewels in a watch, weresubject to molecular heat motion,13 a motion similar to that ofthe molecules of a gas, or of the individual gnats in a cluster ofgnats.These views of Peirce's were received by his contemporarieswith little interest. Apparently only one philosopher noticedthem; and he attacked them.14 Physicists seem to have ignored

12 Collected Papers of Charles Sanders Peirce, 6 1935, 6.44, P. 35. There may ofcourse have been other physicists who developed similar views, but apart fromNewton and Peirce I know of only one: Professor Franz Exner of Vienna. Schro-dinger, who was his pupil, wrote about Exner's views in his book Science, Theoryand Man 1957, PP. 71, 133, 142 f. (This book was previously published under thetitle Science and the Human Temp erament, 1935, and Compton referred to it in Th eFreedom of Man, p. 29.) Cp. also note 25 below.

3 C. S. Peirce, op. cit., 6, 6. 47, P. 37 (first published 1892). The passage,though brief, is most interesting because it anticipates (note the remark on fluc-tuations in explosive mixtures) some of the discussion of macro-effects whichresult from the amplification of Heisenberg indeterminacies. This discussionbegins, it appears, with a paper by Ralph Lillie, Science, 46, 1927, pp. 139 if.,to which Compton refers in The Freedom of Man, p. 50. It plays a considerable partin Compton's book, pp. 48 if. (Note that Compton delivered the Terry Lectures in1931.) Compton, op. cit., note 3, PP- 51 f., contains a very interesting quantitativecomparison of chance effects due to molecular heat motion ( the indeterminacyPeirce had in mind) and Heisenberg indeterminacy. The discussion was carriedon by Bohr, Pascual Jordan, Fritz Medicus, Ludwig von Bertalanffy, and manyothers; more recently especially also by Walter Elsasser, The Phy sical Foundationsof Biology, 1958-14 I am alluding to Paul Carus, Th e Monist 2 1892, pp. 56o if., and 3, 1892,pp. 68 ff.; Peirce replied in Th e Monist 3 1893, pp. 526 if. (see his CollectedPapers, 6, Appendix A, pp. 390 ff.).


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214 Of louds and locksthem;andeventoday most physicistsbelievethat if we hadtoaccept the classical mechanics ofNewtonastrue, weshouldbecompelledtoacceptphysical de term inism, andwithitthepropositionthat allcloudsareclocks. Itwas onlywith thedownfall of classical physicsandwith the rise of the new quan-tumtheorythatphysicistswere preparedtoabandonphysicalde term inism .

Nowthetables wereturned. Indeterminism, whichupto1927hadbeenequatedwithobscurantism,becametherulingfashion; andsomegreat scientists,such asMax Planck,ErwinSchrodinger,andAlbertEinstein, whohesitatedto abandondeterminism,were consideredoldfogies,l althoughtheyhadbeen in the forefrontofthedevelopment of quantumtheory.Imyse lfonc e he ard abri llia nt y oungphy sicist descr ibe Eins te in,who was thenstill alive and hardatwork, asàntediluvian'.Thedelugethat was supposedtohavesweptEinstein awaywasthenewquantumtheory,whichhadrisen during the years from1925to 1927, and towhoseadvent atmost sevenpeoplehadmadecontributionscomparable tothoseof Einstein.

VPERHAPS Imay stop herefora moment to state my ownviewofthesituation, andof scientificfashions.Ibelieve that Peirce

The sudden and complete transformation of the problem-situation may begaugedby the fact that to manyof us oldfogies it does not really seem so very longagothat empiricist philosophers (see for example MoritzSchlick, Al lge m e ineE r k e nntnis lehre , second edn., 1925, p. 277) were physical determinists, while nowa-daysphysical determinism isbeingdismissed byP. H.Nowell-Smith, a giftedandspiritedde fend erof Schlicks, as a n èighte e n th-centu r y b oge y ( M i n d , 63, 1954, P 331see also note 37below). Time marches onand nodoubt it will,in time, solve allour problems, bogiesornon-bogies. Yet oddlyenough we oldfogies seemtorememberthe days of Planck, Einstein, andSchlick,andhavemuch troubleintrying to convince our puzzledandmuddledminds that thesegreat deterministthinkers producedtheirbogies intheeighteenth century, togetherwithLaplacewhoproducedthemost famous bogyof all (thesuper-humanintelligence' ofhisEss ay of 1819, oftencalled 'Laplace's demon'; cp. Compton, The Freed om of M an,pp.5f., and Th e Hu m an M eaningof S cience, p. 34, andAlexander, quotedin note 35,belo w) . Y et a s til l g rea te r e ffo rt m igh t p er ha ps re cal l, e ve n t o o ur fa ili ng m emor ies , asim ilar eighteenth centurybogyproducedby acertain Carus(notthe nineteenth-centurythinker P. Carusreferred to innote 14 but T. L.Carus,whowroteL uc retius d e r e rum n atu r ae ii. 251 -60,quoted byComptoninTh eFreedom of M an, p. 1 .

6. Of CloudsandClocks 21 5wasright inholdingthat allclocksareclouds,to someconsider-able degree-eventhemost preciseof clocks. This,Ithink,isamost important inversionof the mistakendeterminist viewthatall cloudsareclocks. I further believe thatPeirce wasright inholdingthatthisview was compatiblewiththeclassical physicsof Newton.16 I believe thatthisview iseven moreclearlycom-patiblewithEinstein's (special) relativitytheory,andit isstillmore clearly compatible withthenew quantumtheory.In otherwords, I am an indeterminist-like Peirce, Compton, and mostoth er con tem porar y phy sicist s; an dI be liev e,with mos t of them ,that Einstein was mistakenintrying to hold fast to determinism. I may perhapssaythatI discussed this matter withhim, andthat I didnotfindhimadamant.) But Ialsobelievethat thosemodernphysicistswere badlymistakenwhopooh-poohedasantediluvian Einstein's criticismof the quantumtheory.Nobodycan fail to admire the quantumtheory, andEinstein did sowholeheartedly; but hiscriticismofthefashionable interpreta-tionofthetheory-theCopenhageninterpretation-like thecriticismsofferedbydeBroglie, Schrodinger,Bohm,Vigier,andmore recently by Lande,havebeentoolightlybrushedasidebymost physicists.' There are fashionsin science,andsomescientists climbontheband wagonalmostasreadilyas dosomepaintersandmusicians. But althoughfashions and band-wagons mayattracttheweak, theyshouldberesistedrather

16 Ideveloped this viewin 1950ina paperÌndeterminism in Quantum Physicsand in Classical Physics', B ritish Journal for the Philosophy of Sci ence, z , 1950, No. 2,PP. 117-33,andNo. 3, pp.173-95.When writingthis paper I knewnothing,unfortunately, ofPeirce s views (see notes 12and13).I may perhaps mentionhere that I havetakentheideaofopposing clouds and clo ck s from this earlierpaper of mine. Since 1950, whenmy paper was published, thediscussionofindeterminist elements inclassicalphysics has gathered momentum. SeeLeonBrillouin, Scientific Uncertainty and Information, 1964(a bookwithwhichIambynomeans infullagreement),and the referencesto the literature theregiven,especially on pp. 38,105,127, 151f. Tothese references mightbe addedin par-ticular JacquesHadamard s greatpaper concerning geodetic lineson hornedsurfacesof negative c urvature, ,j ou r n al de m ath em atiq u es p u res e t ap p liqu e es , 5th ser ies4, ,898, PP. 27 ff.7 See also mybook Th eL og ic of S cientif ic D iscov ery, especially thenewAppendix*xi;alsochapterixof thisbookwhichcontainscriticismthat is valid inthemain,though, inviewof Einstein scriticismin Appendix *xii,I hadto withdrawthethought experiment (of 1934) described in section77. Thisexperiment can bereplaced, however, bythefamous thought experimentof Einstein, Podolsky, andRosen, discussedthere inAppendix*xi and *xii. See also mypaper `The PropensityInterpretationof theCalculus of Probability,andthe QuantumTheory, inO b s er vatio n and Inter p r e ta tion, ed. by S. Korner, 1957,pp.65-70, and 83-9.

8 437 7


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21 6 f Clouds and Clocksthan encouraged;18 and criticism like Einstein's is always valu-able: one can always learn something from it.

ARTHUR HOLLY COMPTON was among the first who wel-

comed the new quantum theory, and Heisenberg's new physicalindeterminism of 1927. Compton invited Heisenberg to Chicagofor a course of lectures which Heisenberg delivered in the springof 1929. This course was Heisenberg's first full exposition of histheory, and his lectures were published as his first book a yearlater by the University of Chicago Press, with a preface byArthur Compton.19 In this preface Compton welcomed the newtheory to whose advent his experiments had contributed byrefuting its immediate predecessor;20 yet he also sounded a noteof warning. Compton's warning anticipated some very similarwarnings by Einstein, who always insisted that we should notconsider the new quantum theory-'this chapter of the historyof physics', as Compton called it generously and wisely-asbeing `complete'.21 And although this view was rejected byBohr, we should remember the fact that the new theory failed,for example, to give even a hint of the neutron, discovered byChadwick about a year later, which was to become the first ofa long series of new elementary particles whose existence had

8 The last sentence is meant as a criticism of some of the views contained inThomas S. Kuhn's interesting and stimulating book The Structure oScientificRevolut ions 1963. 9 See Werner Heisenberg, The Physical Principles of the Quantum Theory, 1930.20 I am alluding to Compton's refutation of the theory of Bohr, Kramers, andSlater, see note 3 above; see also Compton s own allusion in The Fr e edom of M an,

p. 7 (last sentence), and The Human M eaning of Science, p. 36.2 Cp. Compton's Preface in Heisenberg, op. cit., pp. iii ff.; also his remarks onthe incompleteness of quantum mechanics in The Freedom of Man p. 45 (with areference to Einstein) and in The Human Meaning of Science p. 42. Comptonapproved of the incompleteness of quantum mechanics while Einstein saw in it aweakness of the theory. Replying to Einstein, Niels Bohr asserted (like J. vonNeumann before him) that the theory was complete (perhaps in another sense of theterm). See for example A. Einstein, B. Podolsky, and N. Rosen, Physical Review, 42,1935, pp. 777-80; and Bohr's reply in 48, 1935, pp. 696 ff.; also A. Einstein,Dialec t i ca 2 1948, pp. 32o-4., and Bohr, pp. 312-Ig of the same volume; further,the discussion between Einstein and Niels Bohr in P. A. Schilpp (ed.), AlbertEinste in: Phi losopher -Scient i s t 1949, pp. 201-41, and especially 668-74, and a letterof Einstein's, published in my book, The L ogic of S cientif ic Discovery, pp. 457-64;see also pp. 445-56.

6. Of C louds and Clocks 1 7not been foreseen by the new quantum theory (even though itis true that the existence of the positron could have been derivedfrom the theory of D irac) .22In the same year, 1931, in his Terry Foundation Lectures,5Compton became one of the first to examine the human and,more generally, the biological23 implications of the new indeter-minism in physics. And now it became clear why he had wel-comed the new theory so enthusiastically: it solved for him notonly problems of physics but also biological and philosophicalproblems, and among the latter especially problems connectedwith ethics.

VIITo show this, I shall now quote the striking opening passage ofCompton's The Freedom of Man:

The fundamental question of morality, a vital problem in religion,and a subject of active investigation in science: Is man a free agent?If... the atoms of our bodies follow physical laws as immutableas the motions of the planets, why try? What difference can it makehow great the effort if our actions are already predetermined by

mechanical laws ... ?24Compton describes here what I shall call `the nightmare of the

physical determinist . A deterministic physical clockwork mechan-ism is, above all, completely self-contained: in the perfect deter-ministic physical world there is simply no room for any outsideintervention. Everything that happens in such a world is physi-cally predetermined, including all our movements and thereforeall our actions. Thus all our thoughts, feelings, and efforts canhave no practical influence upon what happens in the physicalworld: they are, if not mere illusions, at best superfluous by-products ('epiphenomena') of physical events.In this way, the daydream of the Newtonian physicist whohoped to prove all clouds to be clocks had threatened to turninto a nightmare; and the attempt to ignore this had led to

See the history of its discovery as told by N. R. Hanson, The Concept of thePos i t r on 1963, chapter ix.

3 See especially the passages on `emergent evolution in The Freedom of Manpp. go ff. ; cp. Th e H u m a n M e a n in g of Science, p. 73-

2 4 Cp. The Freedom of Man, p. 1.


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218 O fC lo uds and Clock ssomething like anintellectual splitpersonality. Compton, Ithink,wasgrateful to thenewquantumtheory for rescuing himfrom this difficult intellectualsituation. Thus hewrites,in T heFreedomof Man: `Thephysicisthasrarely ...botheredhimselfwiththefactthat if ... completelydeterministic . . . laws...apply tomans actions, he is himself an automaton.25And in

he um anM eaning of S cience he e xp resseshis re lief:In my own thinking onthisvital subject I amthusin amuch

more satisfied state of mind than Icould have been atanyearlierstage of science.Ifthe statementsof the laws of physics were assumedcorrect, onewouldhavehadtosuppose (asdid mostphilosophers)that thefeelingoffreedom isillusory, or if [free]choicewerecon-sideredeffective, thatthe statementsof thelawsofphysics were ...unreliable. Thedilemmahas beenan uncomfortable one ...26

Later in the same bookCompton sumsup the situationcrisplyin the words:`... it is no longer justifiableto use physicallawas evidence against humanfreedom27

Thesequotationsfrom Comptonshowclearly that beforeHeisenberg hehad beenharassedbywhatI have here called thenightmare of the physical determinist, andthathe had tried toescapefromthisnightmare byadoptingsomething like anintel-lectual split personality.Or ashe himself puts it: `We [physicists]have preferredmerely topayno attention tothedifficulties.. . 2sCompton welcomed thenewtheory whichrescued him fromallthis.I believe that theonly form of theproblemof determinismwhich is worthd isc ussin gse r ious lyis e xac tly th at p roblemw h ichworried Compton: theproblemwhich arisesfrom a physicaltheorywhich describes the worldas a ph y si ca l ly co m ple te or a

5 Cp. T he Freedom o f M an pp. 26f.; seealso pp. 27f. (thelast paragraph begin-ning on p.27). Imayperhaps remind the reader that my views differ alittlefromthequotedpassage because like. Peirce I think itlogicallypossiblethat thelaws of a systembe Newtonian and so p r im a f acie deterministic) andthe systemnevertheless indeterministic,becausethesystemto whichthe laws apply maybeintrinsicallyunprecise,in thesense, for example, that there isno point insayingthat its co-ordinates, or velocities,are rational (as opposedto irrational) numbers.The followingremark (see Schrodinger, op. cit., p. 143) isalso very relevant:`... theenergy-momentum theoremprovidesus with only four equations, thusleaving theelementaryprocess to agreatextent undetermined,even ifit complieswith them. See also note 16.

p T he H um an M eaningof Science, p. ix.27 Ibid., p.42.26 pThe Freedom of Man,p. 27.

6. Of Clouds and Clocks 21 9physicallyclosed system.29By aphysically closedsystem I meanaset or system ofphysicalent ities,suchas atoms or elementaryparticles or physical forcesor fields of forces,whichinteract witheach other and only with each other-in accordance withdefinitelaws ofinteraction that do not leave any roomforinteractionwith, orinterference by, anything outsidethat closedset or system ofphysicalentities. It is this closure ofthesystemthat createsthe deterministic nightmare.30

VIII

I SHOULDliketo digress here for a minute in orderto contrasttheproblemof physical determinism, whichI consider tobe offundamentalimportance, withthe far fromserious problemwhich many philosophers andpsychologists,following Hume,have substitutedfor it. Hume interpreted determinism(which he called `the doctrineofnecessity , or `the doctrine of constantconjunction )as thedoctrinethat like causes always producelikeeffects and that`likeeffectsnecessarily followfromlikecauses .3 Concerninghuman actions andvolitions heheld, moreparticularly, thatàspectator cancommonlyinfer ouractions fromour motivesandcharacter; and evenwhere he cannot, heconcludes in

9 Assume that ourphysical world is a phy sic ally clo sed systemcontainingchanceelements. Obviouslyit would not bedeterministic; yet purposes,ideas, hopes,and wishescouldnot in such a world have any influence on physical events;assumingthat they exist, they would be completely redundant: they would bewhat arecalledèpiphenomena .(Notethat adeterministic physical systemwill beclosed,but thata closedsystemmaybe indeterministic.Thusìndeterminismisnot enough , as will be explained in sectionx, below; see alsonote40.)

3 Kant suffereddeeply from this nightmareandfailedinhis attempts toescape from it;see Compton s excellentstatementon Kant s avenueof escape inTh e F reedo m of M an pp. 67f. (Inline 2on p.68 thewords ò f Pure Reason should bedeleted.) I may perhaps mention here that I do not agree with everythingComptonhas to sayinthefieldofthephilosophyof science. Examples ofviews I donotshare are: Comptons approval of Heisenberg s positivism or phenomenalism T heFr eedomof M an , p.31), and certain remarks inop. cit., note 7 on p. 20) whichCompton creditsto Carl Eckart: although Newtonhimself was, it seems,not adeterminist (ep. note i s),I donot think that thefairlyprecise idea of phys icalde ter min ism should be discussedin terms ofsomevague`law of causality ;nor do Iagree that Newtonwas aphenomenalist ina sense similar tothat in which Heisen-bergmaybe said to have been aphenomenalist or positivist) in the nineteen-thi rties .

David Hume, A T reatise of Human Nature 1739(ed. L. A. Selby-Bigge,1888andreprints), p. 174;see also, for example, pp. 173and 87.


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22 0 f Clouds and Clocksgeneral, that he might, were he perfectly acquainted with everycircumstance of our situation and temper, and the most secretsprings of our . . . disposition. Now this is the very essence ofnecessity . . ..32 Hume's successors put it thus: our actions, orour volition, or our tastes, or our preferences, are psychologically`caused' by preceding experiences ('motives'), and ultimately byour heredity and environment.

But this doctrine which we may call philosophicalorpsychologicaldetermnismis not only a very different affair fromhysicaldeterminism, but it is also one which a physical determinist whounderstands this matter at all can hardly take seriously. Forthe thesis of philosophical determinism, that Like effects havelike causes' or that Èvery event has a cause', is so vague that itis perfectly compatible with physical indeterminism.

Indeterminism-or more precisely, physical indeterminism-ismerely the doctrine that not all events in the physical world arepredetermined with absolute precision, in all their infinitesimaldetails. Apart from this, it is compatible with practically anydegree of regularity you like, and it does not, therefore, entailthe view that there are èvents without causes'; simply becausethe terms èvent' and `cause' are vague enough to make thedoctrine that every event has a cause compatible with physicalindeterminism. While physical determinism demands completeand infinitely precise physical predetermination and the absenceof any exception whatever, physical indeterminism asserts nomore than that determinism is false, and that there are at leastsome exceptions, here or there, to precise predetermination.Thus even the formula Èvery observable or measurable phys i -cal event has an observable or measurable physical cause' is stillcompatible with physical indeterminism, simply because nomeasurement can be infinitely precise: for the salient pointabout physical determinism is that, based on Newton's dyna-mics, it asserts the existence of a world of absolute mathematicalprecision. And although in so doing it goes beyond the realm ofpossible observation (as was seen by Peirce), it nevertheless istestable, in principle, with any desired degree of precision; andit actually withstood surprisingly precise tests.

By contrast, the formula Èvery event has a cause' says nothingabout precision; and if, more especially, we look at the laws of

Hume, op. cit., pp. 408 f.

6. Of Clouds a n d C l o c k s 21psychology, then there is not even a suggestion of precision. Thisholds for a `behaviourist' psychology as much as for an ìntro-spective' or `mentalist' one. In the case of a mentalist psychologythis is obvious. But even a behaviourist may at the very best predictthat, under given conditions, a rat will take twenty to twenty-two seconds to run a maze: he will have no idea how, by speci-fying more and more precise experimental conditions, he couldmake predictions which become more and more precise-and, inprinciple precise without limit. This is so because behaviourist`laws' are not, like those of Newtonian physics, differential equa-tions, and because every attempt to introduce such differentialequations would lead beyond behaviourism into physiology,and thus ultimately into physics; so it would lead us back to theproblem of physical determinism.As noted by Laplace, physical determinism implies that everyphysical event in the distant future (or in the distant past) ispredictable (or retrodictable) with any desired degree of preci-sion, provided we have sufficient knowledge about the presentstate of the physical world. The thesis of a philosophical (orpsychological) determinism of Hume's type, on the other hand,asserts even in its strongest interpretation no more than that anyobservable difference between two events is related by some as yetperhaps unknown law to some difference-an observable differ-ence perhaps-in the preceding state of the world; obviously avery much weaker assertion, and incidentally one which we couldcontinue to uphold even if most of our experiments, performedunder conditions which are, in appearance èntirely equal', shouldyield different results. This was stated very clearly by Humehimself. Èven when these contrary experiments are entirelyequal', he writes, `we remove not the notion of causes and neces-sity, but ... conclude, that the [apparent] chance ... lies onlyin ... our imperfect knowledge, not in the things themselves,which are in every case equally necessary [i.e., determined], tho'to appearance not equally constant or certain.'33

This is why a Humean philosophical determinism and, more33 Hume, op. cit., pp. 403 f. It is interesting to compare this with pp. 404 f.(where Hume says Ì define necessity two ways') and with his ascription to matter'of `that intelligible quality, call it necessity or not' which, as he says, everybody`must allow to belong to the will' (or `to the actions of the mind'). In other words,Hume tries here to apply his doctrine of custom or habit, and his association

psychology, to `matter ; that is, to physics.


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22 2 OfClouds andClocksespecially, apsychological determinism, lackthestingof physi-caldeterminism.For in Newtonianphysics things really lookedas ifanyapparentlooseness in a system was in fact merelydueto our ignorance, so that, shouldwebe fully informed about thesystem, any appearance ofloosenesswould disappear.Psycho-logy,onthe otherhand, never had this character.Physicaldeterminism,we might sayin retrospect,wasa day-dreamof omniscience whichseemedto become more real withevery advancein physicsuntil it becamean apparentlyin-escapablenightmare. Butthe corresponding daydreams ofthepsychologists were never morethancastles intheair:theywereUtopian dreams ofattainingequality with physics, its mathema-tical methods,and its powerful applications; and perhaps evenofattainingsuperiority, by moulding men and societies. (Whilethese totalitarian dreamsare not seriousfroma scientificpointof view, they are very dangerouspolitically;34butsinceI havedealt withthese dangers elsewhereI donotpropose to discussthe problemhere.)

IHAVE calledphysicaldeterminisma nightmare.It is anight-mare because it asserts that thewhole worldwitheverything initis ahuge automaton, andthat we are nothing but little cog-wheels, or at best sub-automata, withinit.Itthusdestroys,in particular,the idea of creativity. It reduces

toa complete illusion the idea that inpreparing this lectureIhave used mybrain tocreate something new . There was nomorein it, according tophysical determinism, thanthat certainpartsof mybody put down blackmarks onwhite paper: any physicistwithsufficientdetailedinformation couldhavewrittenmy lec-ture bythesimple method of predicting thepreciseplaces onwhichthe physical system consisting of mybody (including mybrain,of course, and my fingers)andmy pen would put downthose black marks.

34 See especiallyB. F.Skinner, W a l d en T w o 1948, a charming and benevolentbut utterly naiveUtopian dreamof omnipotence see especially pp.246-50; also214f.). Aldous Huxley, Br ave N ew W orld 1932 (seeal so Brav e NewWorld R evisited,1959), and George Orwell, rg84 19 48, arewell-knownantidotes. Ihave criticizedsomeof these Utopian andauthoritarianideasin T he O pe n S ociety and Its Enemies,1945, fourthedn., 1962, and in T he Po verty of H ist oricism , e .g., p. g1. Seein bothbooksespecially my criticismof theso-called `sociology of knowledge .)

6. Of Cloudsand Clocks 223Or to usea more impressive example: if physical determinism

isright, then a physicistwhois completelydeaf andwho hasneverheard any musiccouldwrite allthe symphoniesand con-certos written byMozart or Beethoven, by the simple methodof studying theprecisephysical statesof their bodiesandpredict-ingwhere they wouldput down blackmarks - on their linedpaper. Andourdeaf physicist coulddo evenmore: bystudyingMozart sor Beethovensbodieswithsufficient care hecouldwrite scores whichwere neveractuallywritten byMozart orBeethoven butwhich they wouldhave written had certainexternal circumstances of theirlives been different: iftheyhadeatenlamb say instead of chicken ordrunk tea insteadofcoffee.All thiscouldbedonebyour deafphysicist if supplied witha sufficientknowledge ofpurelyphysicalconditions. Therewouldbe no need for him toknow anything about thetheoryofmusic-though hemight be able topredictwhat answersMozartor Beethovenwould have written down under ex am in a-tionconditions if presented with questions onthe theoryofcounterpoint.I believe that allthisis absurd;35 and its absurdity becomeseven moreobvious,I think, when weapply this method ofphysical prediction toa determinist.For according todeterminism, anytheories-suchas, say,determinism-are held because of a certain physical structureoftheholder (perhaps ofhis brain). Accordinglywe are deceiv-ing ourselves(andarephysicallysodetermined astodeceiveourselves) whenever we believethat there are such thingsasargumentsor reasons which makeus accept determinism. Orin

5 My deaf physicist is of c ou rse closel y similar to Laplaces demon (see note 15) ;and Ibelieve thathis achievements areabsurd, simply becausenon-physicalaspects (aims, purposes, traditions,tastes, ingenuity) play arole in the developmentof the physicalworld. or inotherwords, I believe in interactionism (seenotes 43 and62). Samuel Alexander, Space Ti m e and D eity 1920,vol. ii, p.328, says ofwhathecallsthe `Laplacean calculator : `Exceptin thelimited sense described, thehypo-thesis ofthe calculator is absurd. Yet the`limited sen se includes the predictionofall purely physical events, and would thus include the prediction ofthe positionofall theblack mar ksw ritten by Mozart and Beethoven. It excludes only the predictionof mental experience (anexclusion that corresponds closely tomy assumptionofthe physicistsdeafness). Thuswhat I regard as absurd, Alexander is prepared toadmit. (I mayperhaps sayhere that I thinkit preferable to di scu ss the problemoffreedom in connection withthe creation of music or of newscientific theories ortechnicalinventions, ratherthanwith ethics,and ethicalresponsibility.)


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Of Cloudsand Clocksother words,physical determinism isa theory which, ifit is true,isnotarguable, since itmust explain all ourreactions, includingwhat appear tous as beliefs based on arguments, as due to.purely physical conditions Purely physical conditions, includingour physicalenvironment, make us say oraccept whateverwesayor accept;and awell-trainedphysicist who does not knowany French, and whohas never heard of determinism, would beable to predict what aFrenchdeterministwould say in aFrenchdiscussionondeterminism; andofcourse alsowhat his indeter-minist opponent would say. But thismeans that if webelievethat we have accepteda theorylike determinismbecause wewere swayed by the logical forceofcertain arguments, then weare deceivingourselves, accordingtophysicaldeterminism;ormore precisely, weare ina physical condition which determinesus to deceive ourselves.Hume sawmuch ofthis, even thoughit appears that hedidnot quitesee what it meant forhis own arguments; forhe con-fined himselfto comparing thedeterminismof òur judgementswith thatof òur actions , saying that `zee hav e nomore liberty in theone th n in theother .36

Considerations such as these may perhapsbe the reason whythereare somany philosophers who refuse totake the problemof physical determinism seriouslyand dismiss it asa `bogy .37Yet the doctrine that man is m chine wa s a rgu ed m ost forcefullyan dseriou sly in 17 51 longbeforethe theoryo f evolutionb ecamegenerally accepted, byde Lamettrie; andthe theoryof evolu-tion gave theproblem aneven sharper edge, by suggesting thatthere may beno clear distinction betweenlivingmatter anddead matter.38 And in spite of the victoryof the newquantumtheory, and the conversionof somanyphysicists toindetermin-ism,de Lamettrie s doctrine thatman is a machine hastodayperhaps more defenders than ever before amongphysicists,biologists, andphilosophers; especially in the formof the thesisthat manis a computer.39

Humes, op. cit., p. 6og (the italics are mine). See note 15, above, and Gilbert Ryle, The Concept of Mind 1949, pp. 76 if.( The Bogy of Mechanism).8 Cp. N. W. Pirie, `TheMeaninglessnessof theTermsLife and Living ,P er spec tives in B iochemis t r y , 1937(ed. J. Needham and D. E. Green), pp. i I if. 9 Seefor example A.M. Turing, Computing Machineryand Intelligence ,

Mind 59, 1950, PP- 433-60.Turingasserted thatmen.and computersare in

6. Of Clouds an d C locks 22 5Forifweaccept atheory of evolution (such as Darwin s)theneven ifwe remainsceptical about the theorythat lifeemerged

from inorganicmatter we can hardly deny that there must havebeen a time when abstractand. non-physical entities,such asreasonsand arguments and scientificknowledge, and abstractrules,suchas rules forbuilding railwaysor bulldozers or sput-niks or,say, rules of grammar or of counterpoint, did not exist,or at anyrate hadno effect upon thephysicaluniverse. It isdifficult tounderstandhow the physicaluniverse could produceabstract entities such as rules, andthencouldcomeundertheinfluenceof these rules, sothat these rules in their turncouldexert verypalpable effects upon the physicaluniverse.

There is ho wev er at leastone perhaps somewhatevasive butat anyrateeasy way out of this difficulty. Wecan simply denythat these abstract ent ities exist andthat they can influencethephysical universe. Andwe can assert that what do exist are ourbrains, andthat theseare machines likecomputers; thatthealleged ly abs tract r ule sar e p hy sica l e ntit ies ex ac tly like th e c on-cretephysical punch-cards by which we `programme our com-puters; and that the existenceof anything non-physical isjustà nil lus ion , perhaps, and at any rateunimportant, since every-thing would go on as it does even if the re were nosuc hil lusions.According tothis way out, weneednotworryabout the`mental statusof these illusions. Theymay be universalproper-ties of all things: the stone which I throw may have theillusionthat itjumps, justasI havethe illusion thatI throw it; andmypen,or my computer, mayhave theillusion that it worksbecause of its interest inthe problems which itthinksthat it issolving-andwhichI think that I amsolving-whilein factthere is nothing of anysignificance goingonexcept purelyphysical interactions.principleindistinguishable by theirobservable (behavioural) performance,andchallengedhisopponents to sp ify someobservablebehaviouror achievementof man which a computer would in principle be unable to achieve. But this chal-lenge is anintellectual trap: by sp ify ing akind ofbehaviour we would lay downaspecification for building acomputer. Moreover, we use, and build, computersbecause theycan do many thingswhich we cannot do; just as I useapen orpencilwhen I wish to totup a sum I cannot do in my head. `My pencil ismore intelligentthan I, Einstein usedto say.But thisdoes not establish that he is indistinguishablefrom his pencil. (Cp. the final p r gr phs p. 195,of my paper on Indeterminism,referred to innote 16above, andchapter 12, section 5,of my book Conjec tur es andRe futa t ions.


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226 O f Cl ouds a nd C lock sYoumay see fromallthisthat theproblem of physical deter-minismwhichworriedComptonisindeed aserious problem.It is notjust a philosophicalpuzzle, butitaffects atleastphysicis ts , b iolo gists , behaviou rists , psyc holog ists , a nd compu te ren gin eer s.Admittedly, quitea few philosophers havetried toshow(followingHume or Schlick)that it ismerelyaverbal puzzle,apuzzleabout the use of the wordfreedom'. Butthesephilo-sophershave hardly seen the difference between the problemofphysical determinism and thatof philosophical determinism;and they are either determinists likeHume, which explainswhyfor themfreedom' isjustaword', or they haveneverhadthatclose contact withthephysical sciences or with computerengineering which wouldhave impressed upon them thatweare facedwith morethan a merely verbal puzzle.

xLIKEComptonIamamongthose whotaketheproblemofphysicaldeterminismseriously,andlikeComptonIdo notbelieve that we are merecomputingmachines (thoughI readilyadmit thatwecanlearnagreatdealfrom computing machines-evenaboutourselves). Thus,like Compton, I am aphysicalind eterm inist: physical indeterminism,I believe,is anecessaryprerequisitefor any solutionofourproblem. Wehavetobeindeterminists; yet Ishall trytoshow that indeterminismis noteno ugh .Withthisstatement, indeterm inism is n oten ough, Ihave arrived,not merelyat a new point, but atthevery heartofmy problem.Theproblemmay be explainedas follows.If determinismistrue, then thewhole world isaperfectlyrunningflawlessclock, includingallclouds, allorganisms, allanimals, and all men. If,on the otherhand,Peirce's orHeisen-berg'sorsome other formofindeterminismis true, thensheerchance playsa majorrole inourphysical world. B ut is chance reallym oresa ti sf act ory tha nde te rm in ism ?Thequestioniswellknown. Determinists likeSchlickhaveput it inthis way: `... freedomof action, responsibility,andmentalsanity,cannot reach beyond the realmofcausality: they

6. O f C loudsand Cl ock s 227stopwherechancebegins....ahigherdegreeof randomness... [simplymeans] a higher degree ofirresponsibility.'4

Imayperhapsput this idea of Schlick's in termsof an exampleIhave usedbefore:to say thattheblack marks madeonwhitepaper whichIproducedin preparationforthislecturewerejusttheresult of chance is hardly moresatisfactory-thanto say thattheywere physically predetermined. In fact, it is evenless satis-factory.For somepeople mayperhaps bequite readytobelievethatthetext ofmylecture can be inprinciplecompletelyexplained by my physical heredity, andmyphysical environ-ment, includingmy upbringing,thebooks I havebeenreading,andthe talks Ihave listenedto; but hardly anybodywillbelievethatwhat Iamreadingtoyou is the resultofnothingbutchance-justa random sampleof Englishwords,or perhapsof letters,put togetherwithout any purpose, deliberation,plan, or in-tention.The ideathattheonly alternative todeterminism isjust sheerchance was taken overby Schlick, together withmany of hisviewsonthesubject, fromHume,whoassertedthat`theremoval'of whathecalledphysical necessity' must alwaysresult in`thesamething with chance. As objects musteitherbeconjoin'd or not, . . . 'tis impossibleto admit ofanymediumbetwixt chance and an absolute necessity'.41Ishall laterargue againstthisimportantdoctrineaccordingto which the only alternativeto determinismissheer chance.Yet I must admit that thedoctrine seems tohold goodforthequantum-theoretical modelswhichhave been designedtoexplain, or atleast toillustrate,thepossibilityofhumanfree-dom. Thisseems to be thereasonwhy thesemodelsaresoveryunsat isfactory.Comptonhimselfdesigned suchamodel, though hedidnotparticularlylike it. It uses quantumindeterminacy, andtheunpredictabilityof a quantumjump, asamodelof a humandecision ofgreat moment.Itconsistsof anamplifierwhichamplifies the effect ofa single quantum jumpinsuchawaythatit may either causean explosion ordestroy the relaynecessary

4 SeeM.Schlick, Erkenntnis 5,p. 183(extracted from thelasteight lines of thefirstparagraph).4 Hume,op. cit., p. 171.Seealsofor example p.407:`... liberty ...istheverysame thingwithchance.'


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Of Clouds and Clocks Part 1

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