Hume, secret powers, and induction

DONALD SIEVERT

H U M E , S E C R E T P O W E R S , A N D I N D U C T I O N

(Received 6 October 1972)

Hume allegedly raised a problem about induction: predictions are unwarranted because experience and reason provide inadequate foundations for them. 1 Experience cannot be used to justify predictions without cir- cularity: in predicting, we must assume the future will resemble the past, yet in predicting one is, in effect, attempting to establish this resemblance, Reason (demonstration) cannot justify predictions because there is no contradiction in saying things behaved in certain ways until now and will behave differently in the future. According to this view, the amount of information about past and present is irrelevant to our right to predict. Even complete information is insufficient to warrant prediction. 2 How- ever, reexamination of texts reveals that Hume's worry was often different and, not surprisingly, closely tied to other aspects of his philosophy, His worry about predictions can be tied to his scepticism about 'secret powers' or, more generally, unobservable entities. I shall argue that an important Humean point was that we never do or can have complete information about past and present because we are ignorant of 'secret powers', and that it is this ignorance which can render prediction pre-

carious.

The usual so-called problem of induction just sketched presupposes (for the sake of argument) that we have complete information about the past and present. The problem arises because we are able to find neither a demonstration nor a non-circular justification of prediction. That Hume believed a problem of this sort to be serious I do not deny. What I deny is that it is the sole important problem of induction to be found in Hume's writings. Those who assert or imply that it is the sole problem do not do justice to the complexity of Hume's views.

A passage which in a succinct way suggest that Hume's worry about

Philosophical Studies 25 (1974) 247-260. All Rights Reserved Copyright �9 1974 by D. Reidel Publishing Company, Dordrecht-Holland

248 DONALD SIEVERT

induct ion is not the usual one occurs in the 'Abst rac t ' o f the Treatise:

We are determined by CUSTOM alone to suppose the future conformable to the past. When I see a billiard-ball moving towards another, my mind is immediately carry'd by habit to the usual effect, and anticipates my sight by conceiving the second ball in motion. There is nothing in these objects, abstractly considered, and independent of experience, which leads me to form any such conclusion: and even after I have had experience of many repeated effects of this kind, there is no argument, which determines me to suppose, that the effect will be conformable to past experience. The powers, by which bodies operate, are entirely unknown. We perceive only their sensible qualities: and what reason have we to think, that the same powers will always be conjoined with the same sensible qualities. 3

H u m e begins with his view that only cus tom or habit, as opposed to a

method of justification, leads us to prediction. He reminds us that neither

before nor after experience could we justify predictions. Note the reasons

offered. They are that we do no t know ' the powers by which bodies

operate ' and, it is implied, that we have no reason to believe in future

conjunct ions o f those same powers with certain sensible qualities. The

passage suggests that our inability to provide justification for prediction is a funct ion o f ignorance, ignorance o f ' t he powers by which bodies operate. '

This line o f thought occurs also in the Enquiry. Indeed, there the wor ry

about prediction and our ignorance o f 'powers ' are inseparable.

In Section IV of the Enquiry, H u m e raises some sceptical doubts. The

issue which preoccupies h im there is the justification of claims about objects not present to the senses, including predictions about the future. He

believes that all predictions must be based on 4 experience alone (and not on, say, a priori principles). That is, all predictions must be based on

causal principles (correlations or constant conjunctions) discovered by

experience. This is closely related to his description o f the causal relation as one analyzable exclusively in terms o f empirically discoverable rela-

tions. Let us look at two passages f rom Section IV in which he worries about predictions and, in particular, questions their justification. Here is one:

As to past Experience, it can be allowed to give direct and certain information of those precise objects only, and that precise period of time, which fell under its cognizance: but why this experience should be extended to future times.., is the main question on which I wou/d insist. The bread, which I formerly ate, nourished me; that is, a body of such sensible qualities was, at that time, endued with such secret powers: but does it follow that like sensible qualities must always be attended with like secret powers? The consequence seems nowise necessary. At least, it must be acknowledged that there

HUME, SECRET POWERS, AND INDUCTION 249

is here a consequence drawn by the mind; that there is a certain step taken; a process of thought, and an inference, which wants to be explained. (Enquiry, pp. 33-4.)5

I t is this sor t o f passage, coupled with H u m e ' s subsequent s ta tement tha t

nei ther demons t r a t i on no r experience can provide a ' m e d i u m ' which ' en-

ables the mind to d raw such an inference ' , which seems to lead readers to

the usual p r o b l e m of induct ion. Cer ta in ly H u m e is ques t ioning the use

o f pas t experience to jus t i fy predict ions. Yet a closer l o o k reveals someth-

ing else.

H u m e m e n t i o n s ' s e c r e t powers ' . The pred ic t ions which interest h im

are tha t bodies wi th cer ta in sensible quali t ies will also have cer ta in ' secret

powers ' . These pred ic t ions are o f a k ind which eventual ly we mus t t ry to

unders tand . F o r now, however , we m a y ask ; how closely l inked are

H u m e ' s worr ies abou t pred ic t ing the future and this pa r t i cu la r k ind o f

p red ic t ion? I believe that , at least in the Enquiry, as in the passage f rom

the 'Abs t r ac t ' , they are inseparab le : repeatedly , H u m e indicates tha t the

existence and causal role o f ' secret powers ' is a centra l feature o f the

p rob lem.

Several pa r ag raphs later , this becomes clearer. He restates the p r o b l e m

and his sceptical conc lus ion:

Should it be said that, from a number of uniform experiments, we infer a connexion between the sensible qualities and the secret powers; this, I must confess, seems the same difficulty, couched in different terms. The question still recurs, on what process of argument this inference is founded? ... When a man says, I have found, in all past instances, such sensible qualities conjoined with such secret powers: And when he says, Similar sensible qualities will always be conjoined with similar secret powers, he is not guilty of a tautology, nor are these propositions in any respect the same. You say that the one proposition is an inference from the other. But you must confess that the inference is not intuitive; neither is it demonstrative: Of what nature is it, then ? To say it is experimental, is begging the question. For all inferences from experience suppose, as their foundation, that the future will resemble the past, and that similar powers will be conjoined with similar sensible qualities. (Enquiry, pp. 36-7.)

H u m e immedia te ly goes on to state an addi t iona l reason why predic t ions

are precar ious . This add i t ion , coupled with the t a lk o f ' secret powers ' ,

encourages the in te rpre ta t ion I a m urging.

ff there be any suspicion that the course of nature may change, and that the past may be no rule for the future, all experience becomes useless, and can give rise to no inference or conclusion. It is impossible, therefore, that any arguments from experience can prove this resemblance of the past to the future; since all these arguments are founded on the supposition of that resemblance. Let the course of things be allowed hitherto ever so regular; that alone, without some new argument or inference, proves

250 DONALD SIEVERT

not that, for the future, it will continue so. In vain do you pretend to have learned the nature of bodies from your past experience. Their secret nature, and consequently all their effects and influence, may change, without any change in their sensible qualities. This happens some times, and with regard to some objects: Why may it not happen always and with regard to all objects? (Enquiry, pp. 37-8.)

Again, the difficulty involves moving from past (and present) to the future. Again, Hume mentions the difficulty of securing the prediction logically or experientially. Yet towards the end, he introduces an additional argument regarding the latter. He says t h a t / f there is a 'suspicion that the course of nature may change' then experience becomes useless for prediction. He concludes that arguments from experience cannot justify predictions only after stating this conditional. And he goes on to state that the conditional's antecedent is fulfilled: there is a suspicion of the relevant Sort. This puts the problem in a new light. It rests on there being grounds for believing the future may change. What are these grounds ?

Hume says it is change in the 'secret nature' of objects which sometimes does happen and, he seems to conclude, may well happen again in the future. In order to be more specific about this aspect of the problem of prediction I shall indicate further the character and role of the 'secret' aspects of the universe. I shall argue next that Hume thinks there are unknown factors which are involved in complete knowledge of causal happenings.

Hume believes that there are unobservable aspects of the universe. His talk of 'secret powers' and the 'secret nature' of objects is an allusion to these aspects. They are part and parcel of the causal theory of perception Hume sometimes embraces. He asserts from time to time that what we observe, viz., sensible qualities (sense impressions) and collections of such are caused by one's body 6 (and, presumably, its interactions with other bodies). He says, for example, that ". . . all our perceptions are dependent on our organs, and the dispositions of our nerves and animal spirits." 7 Since he says this is true of all perceptions, it follows that all we observe is causally related to a body. Bodies, therefore, influence what we observe. In other words, they have the power to affect, and do affect, observables. Our inability to observe bodies, the causes of our impressions, precludes knowledge of bodies and, therefore, knowledge of the connections between what we observe and them.

But as no beings are ever present to the mind but perceptions; it follows that we may


observe a conjunction or a relation of cause and effect between different perceptions, but can never observe it between perceptions and objects [bodies]. 'Tis impossible, therefore, that from the existence or any qualities of the former, we can ever form any conclusion concerning the existence of the latter, or ever satisfy our reason in this particular. (Treatise, p. 212.)

Thus the na ture of bodies, as well as their influence on what we observe,

is unknowable . No t inappropriately, Hume refers to the 'secret na tu re '

and 'secret powers ' of bodies.

Tha t bodies consti tute a vast area of ignorance for us, H u m e leaves no

doubt . A recurrent theme in his writings is that a significant por t ion of

the universe is no t knowable. Consider these passages:

It must certainly be allowed, that nature has kept us at a great distance from all her secrets, and has afforded us only the knowledge of a few superficial qualities of objects; while she conceals from us those powers and principles on which the influence of those objects entirely depends. Our senses inform us of the color, weight, and con- sistence of the bread; but neither sense nor reason can ever inform us of those qualities which fit it for the nourishment and support of a human body. (Enquiry, pp. 32-3.)

It is confessed, that the utmost effort of human reason is to reduce the principles, productive of natural phenomena, to a greater simplicity, and to resolve the many particular effects into a few general causes .... But as to the causes of these general causes, we should in vain attempt their discovery; nor shall we ever be able to satisfy ourselves, by any particular explication of them. These ultimate springs and principles are totally shut up from human curiosity and inquiry. Elasticity, gravity, cohesion of parts, communication of motion by impulse; these are probably the ultimate causes and principles which we shall ever discover in nature; and we may esteem ourselves sufficiently happy if, by accurate enquiry and reasoning, we can trace up the particular phenomena to, or near to, these general principles. The most perfect philosophy of the natural kind only staves off our ignorance a little longer .... (Enquiry, pp. 30-1.)

These passages are of interest part ly because they reveal Hume ' s commit-

ment to the posi t ion that there is a 'na ture in itself ' about which we are

ignoran t in m a n y ways. s Its general character, so far as we can know it,

is mathematical . More than that Hume will no t say because he believes

we can know no more.

The passages are of interest for another reason as well. I n both, H u m e

suggests that the par t of na ture which is u n k n o w n to us has a causal role

in the 'p roduc t ion of na tura l phenomena . ' I n the first, the fact tha t the

qualities of bread which nour ish us are u n k n o w n is used to illustrate how

little we do and can know about such seemingly wel l -known happenings

as nour ishment . The 'secrets' of na ture seem to include u n k n o w n qualities

of objects which play a role in causal series of events. In the second, what

252 D O N A L D S I E V E R T

is unknown are certain general 'causes and principles' which are 'pro-

ductive of natural phenomena'.

The view that unknowns of the sort just considered are somehow inte-

gral albeit unknown parts of the causal fabric of the universe is indicated elsewhere by Hume. For example, in describing the imaginary case of

someone's being brought into the world suddenly, Hume contrasts what

such a person could and could not find out about causal happenings. Such a person

... would, indeed, immediately observe a continual succession of objects, and one event following another; but he would not be able to discover anything farther. He would not, at first, by any reasoning, be able to reach the idea of cause and effect; since the particular powers, by which all natural operations are performed, never appear to the senses ....

Suppose, again, that he has acquired more experience, and has lived so long in the world as to have observed familiar objects or events to be constantly conjoined to- gether; what is the consequence of this experience? He immediately infers the existence of one object from the appearance of the other. Yet he has not, by all his experience, acquired any idea or knowledge of the secret power by which the one object produces the other .... (Enquiry, p. 42.)

The case is a fairly straightforward illustration of Hume's general view

that prior to (a series of) experience(s), a person would not only not have

the idea of causal connection in specific cases; he would not have the

idea of causal connection at all. After experience, however, he would

have the idea and would make causal inferences. Hume indicates that

such inferences would not be a matter of reasoning. He goes on to appeal to what he calls Custom or Habit as the "principle which determines him

to form such a conclusion". (Enquiry, p. 43.)

What is striking about the last passage is Hume's mention of the "par-

ticular powers, by which all natural operations are performed" and "the

secret power by which the one object produces the other." He implies that all cases of causation involve 'secret powers'. To be sure, what is known in such cases is the constant conjunction of instances of kinds of things and/or events. However, according to Hume, also present is the influence of unknown 'powers'. Thus Hume is maintaining that, on the

one hand, experience reveals causal connections (only) in so far as the constant conjunctions are revealed. On the other hand, what experience

does not reveal to us are the "particular powers by which all [!] natural operations are performed".

ItUME, SECRET POWERS, AND I N D U C T I O N 253

What are these 'powers' which experience does not reveal? I suspect

that what is not revealed are a host of what we would call intervening

variables in causal sequences. That is, 'between' certain constantly con-

joined things or events are other things or events necessary for the constant conjunction to occur and yet unknown by us. Hume illustrates this

appeal to intervening variables in the midst of his discussion of powers

when he deals with the case of volition. 9 One of the points which recurs

is that we do not and perhaps can not know all the elements in the series of events which occur between my deciding to move a limb and the limb's

moving. What we do not know is the "secret mechanism or structure of parts, upon which the effect depends." (Enquiry, pp. 68-9.) He makes

the point, in more detail, in another way:

We learn from anatomy, that the immediate object of power in voluntary motion, is not the member itself which is moved, but certain muscles, and nerves, and animal spirits, and, perhaps, something still more minute and more unknown, through which the motion is successively propagated, ere it reach the member itself whose motion is the immediate object of volition .... Here the mind wills a certain event. Im- mediately another event, unknown to ourselves, and totally different from the one intended, is produced: This event produces another, equally unknown: Till at last, through a long succession, the desired event is produced .... That their [i.e., limbs'] motion follows the command of the will is a matter of common experience, like other natural events: But the power or energy by which this is effected, like that in other natural events, is unknown and inconceivable. (Enquiry, pp. 66-7.)

Hume again calls attention to the fact that while the conjunction of voli-

tion and limb-motion is well established, the relevant intervening variables

are unknown. And, he makes clear, the point is general: it pertains to

other natural events as well.

I have been arguing that Hume believes both that there is a part of

nature which is unknown to us and that this part of nature is a causally

relevant factor in (explaining) the occurrence of conjunctions which are known to us. 1~ With these two views in mind, let us return to the passages

and the problem of induction with which I began. Hume says that change in the 'secret nature' of objects sometimes does

occur and suggests that such change may well happen again. The example he gives is that of things which to all appearances are pieces of bread but

which do not consistently provide nourishment. His explanation is that they vary in their 'secret powers'. Because we are not in a position to

establish that what looks, smells, tastes, etc., like bread has the secret

254 DONALD SIEVERT

power on which nourishment depends, we are not in a position to predict that a given bread-like object will nourish us. Nor is this kind of case unusual in general or in Hume's discussion in particular. Elsewhere, he mentions other cases in which anticipated effects of given causes do not occur because intervening variables do vary, unbeknownst to us, from time to time: volitions do not always effect the desired consequences (Enquiry, p. 68), rhubarb is not always a purge, opium a soporific (En- quiry, pp. 58-9), etc. Such cases give rise to the general point I want to make.

As we saw, Hume believes that 'secret powers' are relevant variables in cases of causation and he believes they are unknowable. One implica- tion is that we do not and can not have complete knowledge of causal happenings. Another claim (which he suggests in the texts cited at the outset) is that we may not predict (although as a matter of psychological fact we do make predictions) because of this ignorance about the nature of bodies. In short, one may not predict because one is (and will remain) ignorant of (the values of) certain relevant variables. Put differently, Hume is saying: there is no known correlation between sensible qualities and 'secret powers'. Indeed, we know that the same sensible qualities are often correlated with varying 'secret powers'. 11 Therefore, sensible qualities are no guide to the 'secret powers' of bodies. 12 Hence where a prediction requires knowledge of such powers, we are at a loss because of our ignorance of them. Since this is our position, in principle, with regard to every prediction, all predictions may be viewed as precarious. Hume thus calls attention simultaneously to our ignorance of such powers and to their relevance in undermining prediction.

The usual problem, sketched at the outset, presupposes that we have complete information about past and present. The alleged problem is that even complete information is not sufficient information for justified prediction. I have argued that the problem Hume is raising is different. It is that we never do have complete information about causal happenings and this fact explains why such limited knowledge of causal happenings as we do have is insufficient for warranting predictions. In short, it is our ignorance which poses a problem for prediction.

Hume does not suggest methods by which our ignorance of nature's 'secrets' may be eliminated. In other words, he does not indicate how incomplete knowledge could be made more complete in the relevant way.


On the contrary, he emphasizes that 'neither sense nor reason' can inform

us of 'secret powers' and that "the most perfect philosophy of the natural kind only staves off ignorance a little longer" (Enquiry, p. 31). Given what Hume takes to be ultimate and inescapable ignorance, the force of the argument I am emphasizing is equal to that of the usual one: predictions are unwarranted even if customarily made. The force of the argument concerning ignorance derives from Hume's basically sceptical epistemology and representationalist ontology. Roughly speaking, what I mean by this is that Hume believes that all we can know is what we can directly perceive and he also believes that the universe contains additional factors which are unperceivable and causally relevant in all cases. Obviously, not everyone wants to adopt the Humean gambits on which the argument depends.

II

In this section I shall indicate the position Hume thinks we would be in if, per impossible, we did have knowledge of secret powers and defend the interpretation I offer against the charge that I reintroduce the notion of power which, after all, is a notion Hume argues against.

It would seem that if, as I have argued, one problem of prediction in Hume is our ignorance of 'secret powers' , then Hume ought to maintain that we would be in a better position to make predictions if we had knowledge of secret powers. In more than one place, Hume indicates precisely this. One of the main points of the Dialogues Concerning Natural Religion is that those who believe that things happen either by chance or by design assume a false dichotomy. Hume proposes a third alternative, viz., things happen according to causal laws. (How he uses this point to undermine theological inferences need not concern us). What is relevant is that Hume at least suggests that if we knew the kinds of things we do not know, viz., the 'secret aspects' of nature, then we could predict most accurately the course of nature. He says:

It is observed by arithmeticians, that the products of 9 compose always either 9 or some lesser product of 9 .... To a superficial observer, so wonderful a regularity may be admired as the effect either of chance or design; but a skilful algebraist immediately concludes it to be the work of necessity, and demonstrates, that it must for ever result from the nature of these numbers. Is it not probable, I ask, that the whole economy of the universe is conducted by a like necessity, though no human algebra can furnish a key which solves the difficulty? And instead of admiring the order of natural beings,

256 DONALD SIEVERT

may it not happen, that could we penetrate into the intimate nature of bodies, we should clearly see why it was absolutely impossible, they could ever admit of any other disposition? (Dialogues, p. 191.) 1~

N o r is the passage an isolated one. Hume makes the same point elsewhere

in the Dialogues when he says:

Chance has no place, on any hypothesis, sceptical or religious. Every thing is surely governed by steady, inviolable laws. And were the inmost essence of things laid open to us, we should then discover a scene, of which, at present, we can have no idea. Instead of admiring the order of natural beings, we should clearly see, that it was absolutely impossible for them, in the smallest article, ever to admit of any other disposition. (Dialogues, pp. 174-75.)

H u m e is suggesting a species o f determinism. According to it all events

happen according to causal law(s): for every event, there is a set o f antecedent condit ions and one or more laws such that a causal explanation

o f the event is possible. Briefly, the universe is lawful th rough and through.

Epistemologically speaking, this amounts to the view t h a t / f one knew

all matters o f individual fact and all true generalities (laws), then one could accurately predict all other events. 14

Such determinism recurs in Hume ' s discussions o f liberty. In those dis-

cussions, H u m e mentions predictability o f all occurrences and asserts

that with knowledge of 'secret ' variables, one could predict, a m o n g other

things, our actions:

And it seems certain, that, however we may imagine we feel a liberty within ourselves, a spectator can commonly infer our actions from our motives and character; and even where he cannot, he concludes in general, that he might, were he perfectly acquainted with every circumstance of our situation and temper, and the most secret springs of our complexion and disposition. (Treatise, p. 409; Enquiry, p. 94.)

Such passages leave no doubt that H u m e believes t h a t / f w e were in pos- session o f knowledge of the 'secret ' aspects o f the universe, then our posit ion regarding predict ion would not only be rather different f rom our actual one but, in addition, would enable complete and accurate pre-

diction. This is the first point I wanted to make. Does Hume, by appeal to secret powers, invoke the kind o f powers

against which he argues so strenuously? I do not think so. The not ion o f power against which he argues is one according to which there are qualities such that, i f we know an object to have one o f them, one can determine f rom that fact alone what effect it will have in its interaction


wi th o ther objects, x5 Tha t is, H u m e th inks o f powers as character is t ics

which determine, necessarily, the effects of the in terac t ion o f bodies ex-

hibi t ing those character is t ics wi th o ther bodies. In effect, as H u m e sees it,

to believe in this (object ionable) no t ion o f power is to believe in necessary

connec t ions a m o n g causal ly re la ted objects. The view I ascr ibe to h im

does no t involve powers in this sense. As I ind ica ted in the first part o f

the paper , ' secret powers ' are re levant in tervening var iables which, as i t

happens , are unknown. Asser t ing tha t they are involved in comple te

knowledge o f causal happenings does not imply tha t they are involved in

o r p rov ide necessary connect ions. I suspect tha t H u m e believes tha t i f we

had knowledge o f them, wha t we would know is new cons tan t conjuc-

t ions in some cases, add i t iona l conjuncts of pa r t i a l ly k n o w n cons tan t

conjunc t ions in others. Recal l the numerous in tervening states he th inks

are involved in a vol i t ion ' s being effective. I f known, they would show us

tha t the con junc t ions involved in vol i t ions ' being effective are more com-

plex then we had realized. K n o w i n g them would no t involve knowing a

new k ind o f connect ion. 16

University o f Missouri, Columbia

NOTES

1 See, for example, A. J. Ayer, Language Truth and Logic, Dover Publications, Inc., New York, 1952, pp. 49-50; N. Goodman, Fact, Fiction and Forecast, Bobbs-Merrill Co., Inc., Indianapolis 1965, p. 59; K. R. Popper, Conjectures and Refutations, Basic Books, New York, 1962, p. 42; F. L. Will, 'Will the Future Be Like the Past? MitM LVI (1947) 332-47.

This view can be expressed by saying that all or complete information is as good as none when it comes to predicting the future. Hume suggests this view by saying that "... all experience becomes useless, and can give rise to no inference or conclusion." See D. Hume, Enquiries Concerning the Human Understanding and Concerning the Principles of Morals (ed. by L. A. Selby-Bigge), The Clarendon Press, Oxford, 1951, p. 38. All references to the Enquiry will be to this edition. a D. Hurne, Abstract of a Treatise of Human Nature (ed. by J. M. Keynes and P. Sraffa), Cambridge University Press, 1938, p. 16. It is worth noting that D. Stove, in an ex- cellent paper on Hume and induction, appeals to the 'Abstract'. He calls attention to the same passage and argues, persuasively, that it deserves more scrutiny than it has received. While he, too, argues that Hume's point is not what many commentators have taken it to be, he ignores the concluding two sentences, the ones mentioning secret powers; indeed, he implies that they are not part of the argument. His paper, 'Hume, Probability, and Induction' appears in The Philosophical Review LXXIV (1965) 160-177. 4 'Based on' is ambiguous, as Humes comes to emphasize. It may mean either justified

258 D O N A L D SIEVERT

by experience or caused by experience. While I-Ittme doubts that experience justifies predictions, he retains the claim that it causes us to make predictions. In this latter sense he never doubts that predictions, and claims about absent objects generally, are based on experience. 5 Notice that Hume wonders whether the claims that other bread must nourish us and that similar sensible qualities must always be conjoined with the same secret powers can be justified. Taken literally, he seems to be asking whether we may believe in certain necessary connections. Whether we should take him literally, and hence whether we should view him as concerned here with necessary connections, I can not determine. Perhaps the terminology merely expresses his general concern with necessary connections. 6 D. I-Iume, A Treatise o f Human Nature (ed. by L. A. Selby-Bigge), Clarendon Press, Oxford, 1928, p. 211. All references to the Treatise w~.ll be to this edition. 7 Of course, Hume's scepticism about the view that there are unknown bodies varies from time to time and from mood to mood, as he himself admits. Sometimes he denies that we have any right to hold such a view, even if we are psychologically compelled to hold it. s Galileo and Locke, who also held that the nature of the physical world is mathematical, express in very similar terms our ignorance of it. In Galileo's Letters on Sunspots [sections (translated by S. Drake) appear in The Philosophy o f the Sixteenth and Seventeenth Centuries (ed. by R. Popkin), The Free Press, New York, 1966] Galileo says:

... In our speculating we either seek to penetrate the true and internal essence of natural substances, or content ourselves with a knowledge of some ~f their properties. The former I hold to be as impossible an undertaking with regard to the closest elemental substances as with more remote celestial things. The substances composing the earth and the moon seem to me to be equally unknown, as do those of our elemental clouds and of sunspots. I do not see that in comprehending substances near at hand we have any advantage except copious detail; all the things among which men wander remain equally unknown, and we pass by things both near and far with very little or no real acquisition of knowledge. When I ask what the substance of clouds may be and am told that it is a moist vapor, I shall wish to know in turn what vapor is. Peradventure I shall be told that it is water, which when attenuated by heat is resolved into vapor. Equally curious about what water is, I shall then seek to find that out, ultimately learning that it is this fluid body which runs in our rivers and which we constantly handle. But this final information about water is no more intimate than what I knew about clouds in the first place; it is merely closer at hand and dependent upon more of the senses. In the same way I know no more about the true essences of earth or fire than about those of the moon or sun, for that knowledge is withheld from us, and is not to be understood until we reach the state of blessedness.

Cf. John Locke, in the Essay Concerning Human Understanding, Fraser edition Dover Publications, Inc., New York, 1959, Vol. II, Book IV, Chapter Ill , Section 24, p. 215:

As the want of ideas which our faculties are not able to give us shuts us wholly from those views of things which it is reasonable to think other beings, perfecter than we, have, of which we know nothing; so the want of ideas I now speak of keeps us in ignorance of things we conceive capable of being known to us. Bulk, figure, and motion we have ideas of. But though we are not without ideas of these primary qualities of bodies in general, yet not knowing what is the particular bulk, figure, and motion,

HUME~ SECRET POWERS~ AND I N D U C T I O N 259

of the greatest part of the bodies of the universe, we are ignorant of the several powers, etticacies, and ways of operation, whereby the effects which we daily see are produced.

9 It is worth noting that one reason Hume discusses the case of volition at length is that some philosophers apparently believed that an idea of power might be derived from cases involving (effective) volitions. They thought, as Hume sees it, that volitions necessarily effect certain bodily activities. Hume insists that the case of effective volition is no different from any other: what effect a volition will have can be known only by experience. One discovers in the relevant experiences constant conjunction at most. Thus the 'power' of volitions to affect bodies turns out to be merely another instance of constant conjunction. I-Iume denies that any other notion of power is intelligible and available. 10 Robert Paul, in 'Appearances and Expectations', Mind N.S. LXXVIII (1969) 342-353, is intrigued by some of the same passages and tendencies in Hume as I am. Yet he uses them in a different way: he argues that Hume's attempts to characterize the problem of induction are 'self-defeating' with the result that Hume's misgivings about inferences from the past to the future become 'unintelligible'. n That is, we know that certain one-to-one correlations do not obtain: sensible qualities occur once with one set of 'secret powers', then with another. 18 Hume may well be worried about what might now be called dispositional qualities: being flammable, being brittle, etc. Surely such qualities are relevant variables in numerous cases of causation and their presence is often not readily determined by a cursory examination of sensible qualities. lz D. Hume, Dialogues Concerning Natural Religion (ed. by Norman Kemp Smith), Thomas Nelson and Sons, Ltd., London, 1947, p. 191. Subsequent reference is to this edition. 14 Several comments are in order. First. Needless to say, this view involves an ideal rather than an actual possibility. One might say, with an eye toward Kant and ideal situations, that Hume in effect appeals to a regulative idea. Consider also footnote eight: Galileo describes the position in which we could have such knowledge as a 'state of blessedness'; Locke speaks of 'beings more perfect than we' who might have such knowledge. Second. Hume talks about 'absolute impossibility' in the passages from the Dialogues. I assume he is referring to the deductive necessity with which certain statements follow from others. When he says that with fuller knowledge of the universe we would see that things could not be otherwise, he may be read as saying: i f one knew all matters of fact and all true generalities up until a given time, then one could infer, deductively, true statements about the future course of nature. All the statments of the deduction, given Hume's general views, are contingent nonetheless. The necessity lies in the (validity of the) deduction, not in the facts. Third. Obviously, I only allude to numerous notions and distinctions in the philosophy of science. For elaboration, see G. Bergmann, Philosophy of Science, University of Wisconsin Press, Madison, 1959 and Stove's article, op. cit. Fourth. Steven Schwarzschild, one of several co/leagues who read an earlier draft, suggests that the 'secrets' of nature are to Hume's epistemology what God is to Hume's theology in the Dialogues: they complete Hume's view of the total situation but are beyond our epistemological reach, so to speak. Bc, th God (in the limited sense Hume indicates at the end of the Dialogues) and the 'secrets' determine 'order ' which Hurne explicates in terms of lawfulness. (I also thank Carl Wellman. His forceful criticisms of an earlier draft led me to make numerous alterations.) 15 Cf., Treatise, p. 161 : " I f we be possest, therefore, of any idea of power in general,

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we must also be able to conceive some particular species of it, and as power cannot subsist alone, but is always regarded as an attribute of some being or existence, we must be able to place this power in some particular being, and conceive that being as endow'd with a real force and energy, by which such a particular effect necessarily results from its operation." 16 Obviously there remains the issue of the relation of the passages I have cited (including that from the Treatise 'Abstract ') to those in the Treatise proper. To deal with it, one would have to spell out some view of the relation of the Enquiry and the Treatise in general and on the issue of induction in particular. About that relation I am not sure. The discussion of the Treatise usually cited proceeds on the assumption (stated in the ' Introduction' , p. xxi) that we are, and will remain, ignorant of the 'secret powers' of nature. Therefore the question of what Hmne would say, at the time he wrote the Treatise, about the (ideal) situation in which we had knowledge of them may be moot. (At the same time, there is the passage cited above from the discussion of liberty which indicates that if we knew more than we do and can know, all our actions would be predictable.)

It is perhaps worth noting that my interpretation, though it provides a more complex view of prediction in Httme than the usual one, is consistent with a main point of the Treatise, viz., that there is no 0ogical) necessity about the course of nature. The laws of nature and/or particular facts of nature could, logically speaking, change at any time. In other words, statements expressing lawful generalities and individual matters of fact are contingent. The interpretation advanced here does not presuppose that there are necessary connections in nature.

Concerning this last point, I-Iume makes explicit appeal to regularity and constancy when discussing unknown causes in his The Natural History of Religion, Stanford University Press, Stanford, 1957, pp. 28-9:

We are placed in this world, as in a great theatre, where the true springs and causes of every event are entirely concealed from us .... These unknown causes, then, become the constant object of our hope and fear .... Could men anatomize nature, according to the most probable, at least the most intelligible pholisophy, they would find, that these causes are nothing but the particular fabric and structure of the minute parts of their own bodies and of external objects; and that, by a regular and constant machinery, all the events are produced, about which they are so much concerned.

There is no suggestion that the introduction of unknown causes involves the introduc- t ion of necessary connections. Indeed, the appeal merely to regularity and constancy suggests the contrary. For a view of Hume as a believer in necessary connections among unknown causes, see R. F. Anderson's Hume's First Principles, University of Nebraska Press, Lincoln, 1966. See also the second comment in note 14 above.

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Hume, secret powers, and induction