The Works of George Berkeley Part 61

In all this it can hardly be said that Berkeley has in this adequately sounded the depths of Causation. He proclaims inability to find through his senses more than sequence of significant sensuous appearances, which are each and all empty of active power; while he apparently insists that he _has_ found active power in the mere _feeling __ of exertion_; which after all, as such, is only one sort of antecedent sign of the motion that is found to follow it. This is still only sequence of phenomena; not active power. But is not causation a relation that cannot be truly presented empirically, either in outer or inner consciousness? And is not the Divine order that is presupposed by us in all change, a presupposition that is inevitable in trustworthy intercourse with a changing universe; unless we are to confess _atheistically_, that our whole sensuous experience may in the end put us to utter confusion? The pa.s.sive, uneasy feeling of strain, more or less involved in the effort to move our bodies and their surroundings, is no doubt apt to be confused with active causation; for as David Hume remarks, "the animal _nisus_ which we experience, though it can afford no accurate precise idea of power, enters very much into the vulgar, inaccurate idea which is formed of it." So when Berkeley supposes that he has found a concrete example of originating power in the _nisus_ of which we are conscious when we move our bodies, he is surely too easily satisfied. The _nisus_ followed by motion is, _per se_, only a natural sequence, a caused cause, which calls for an originating cause that is _absolutely_ responsible for the movement. Is not the index to this absolutely responsible agency an ethical one, which points to a free moral agent as alone necessarily connected with, or responsible for, the changes which _he can_ control? Persons are causally responsible for their own actions; and are accordingly p.r.o.nounced good or evil on account of acts of will that are not mere caused causes-pa.s.sively dependent terms in the endless succession of cosmical change. They must originate in self, be absolutely self-referable, in a word supernatural issues of the personality. Moral reason implies that they are not determined _ab extra_, and so points to moral agents as our only concrete examples of independent power; but this only so far as those issues go for which they are morally responsible. Is not faith in the Universal Power necessarily faith-venture in the absolutely perfect and trustworthy moral agency of G.o.d?

While the principle of Causation, in its application to change of place on the part of bodies and their const.i.tuent atoms, is the leading thought in the _De Motu_, this essay also investigates articulately the nature of the phenomenon which we call _motion_ (sect. 43-66). It a.s.sumes that motion is only an effect, seeing that no one who reflects can doubt that what is presented to our senses in the case of motion is altogether pa.s.sive: there is nothing in the successive appearance of the same body in different places that involves action on the part of either of the moving or the moved body, or that can be more than inert effect (sect. 49). And all concrete motion, it is a.s.sumed, must be something that can be perceived by our senses. Accordingly it must be a perceptible _relation between bodies_, as far as it is bodily: it could make no appearance at all if s.p.a.ce contained only one solitary body: a plurality of bodies is indispensable to its appearance. Absolute motion of a solitary body, in otherwise absolutely empty s.p.a.ce, is an unmeaning abstraction, a collocation of empty words. This leads into an inquiry about relative s.p.a.ce as well as relative place, and the intelligibility of absolute s.p.a.ce, place, and motion (sect. 52-64).

Local motion is unintelligible unless we understand the meaning of _s.p.a.ce_. Now some philosophers distinguish between absolute s.p.a.ce, which with them is ultimately the only real s.p.a.ce, and that which is conditioned by the senses, or relative. The former is said to be boundless, pervading and embracing the material world, but not itself presentable to our senses; the other is the s.p.a.ce marked out or differentiated by bodies contained in it, and it is in this way exposed to our senses (sect. 52).

What must remain after the annihilation of all bodies in the universe is relativeless, undifferentiated, absolute s.p.a.ce, of which all attributes are denied, even its so-called extension being neither divisible nor measurable; necessarily imperceptible by sense, unimaginable, and unintelligible, in every way unrealisable in experience; so that the words employed about it denote _nothing_ (sect. 53).

It follows that we must not speak of the real s.p.a.ce which a body occupies as part of a s.p.a.ce that is necessarily abstracted from all sentient experience; nor of real motion as change within absolute s.p.a.ce, without any relation between bodies, either perceived or conceived. All change of place in one body must be relative to other bodies, among which the moving body is supposed to change its place-our own bodies which we animate being of course recognised among the number. Motion, it is argued, is unintelligible, as well as imperceptible and unimaginable, without some relation between the moving body and at least one other body: the truth of this is tested when we try to suppose the annihilation of all other bodies, our own included, and retain only a solitary globe: absolute motion is found unthinkable. So that, on the whole, to see what motion means we must rise above the mathematical postulates that are found convenient in mechanical science; we must beware of empty abstractions; we must treat motion as something that is real only so far as it is presented to our senses, and remain modestly satisfied with the perceived relations under which it then appears (sect. 65-66).

Finally, is motion, thus explained, something that can be spoken of as an ent.i.ty communicable from one body to another body? May we think of it as a datum of sense existing in the striking body, and then pa.s.sing from it into the struck body, the one losing exactly as much as the other receives? (sect. 67). Deeper thought finds in those questions only a revival of the previously exploded postulate of "force" as _something sensible_, yet distinct from all the significant appearances sense presents. The language used may perhaps be permitted in mathematical hypotheses, or postulates of mechanical science, in which we do not intend to go to the root of things. But the obvious fact is, that the moving body shews less perceptible motion, and the moved body more. To dispute whether the perceptible motion acquired is numerically the same with that lost leads into frivolous verbal controversy about Ident.i.ty and Difference, the One and the Many, which it was Berkeley's aim to expel from science, and so to simplify its procedure and result. Whether we say that motion pa.s.ses from the striking body into the struck, or that it is generated anew within the struck body and annihilated in the striking, we make virtually the same statement. In each way of expression the facts remain, that the one body presents perceptible increase of its motion and the other diminution. Mind or Spirit is the active cause of all that we then see.

Yet in mechanical science-which explains things only physically, by shewing the significant connexion of events with their mechanical rules-terms which seem to imply the conveyance of motion out of one body into another may be pardoned, in consideration of the limits within which physical science is confined, and its narrower point of view. In physics we confine ourselves to the sensuous signs which arise in experience, and their natural interpretation, in all which mathematical hypotheses are found convenient; so that gravitation, for example, and other natural rules of procedure, are spoken of as _causes_ of the events which conform to them, no account being taken of the Active Power that is ultimately responsible for the rules. For the Active Power in which we live, move, and have our being, is not a datum of sense; meditation brings it into light. But to pursue this thought would carry us beyond the physical laws of Motion (sect. 69-72).

The _De Motu_ may be compared with what we found in the _Principles_, sect. 25-28 and 101-117. The total powerlessness of the significant appearances presented to the senses, and the omnipotence of Mind in the economy of external nature, is its chief philosophical lesson.

De Motu

1. Ad veritatem inveniendam praecipuum est cavisse ne voces males intellectae(925) n.o.bis officiant: quod omnes fere monent philosophi, pauci observant. Quanquam id quidem haud adeo difficile videtur, in rebus praesertim physicis tractandis, ubi loc.u.m habent sensus, experientia, et ratiocinium geometric.u.m. Seposito igitur, quantum licet, omni praejudicio, tam a loquendi consuetudine quam a philosphorum auctoritate nato, ipsa rerum natura diligenter inspicienda. Neque enim cujusquam auctoritatem usque adeo valere oportet, ut verba ejus et voces in pretio sint, dummodo nihil clari et certi iis subesse comperiatur.

2. Motus contemplatio mire torsit veterum philosophorum(926) mentes, unde natae sunt variae opiniones supra modem difficiles, ne dicam absurdae; quae, quum jam fere in desuetudinem abierint, haud merentur ut iis discutiendis nimio studio immoremur. Apud recentiores autem et saniores hujus aevi philosophos(927), ubi de Motu agitur, vocabula haud pauca abstractae nimium et obscurae significationis occurrunt, cujusmodi sunt _solicitatio gravitatis_, _conatus_, _vires mortuae_, &c., quae scriptis, alioqui doctissimis, tenebras offundunt, sententiisque non minus a vero, quam a sensu hominum communi abhorrentibus, ortum praebent. Haec vero necesse est ut, veritatis gratia, non alios refellendi studio, accurate discutiantur.

3. _Solicitatio_ et _nisus_, sive _conatus_, rebus solummodo animatis revera competunt(928). c.u.m aliis rebus tribuuntur, sensu metaphorico accipiantur necesse est. A metaphoris autem abstinendum philosopho. Porro, seclusa omni tarn animae affectione quam corporis motione, nihil clari ac distincti iis vocibus significari, cuilibet constabit qui modo rem serio perpenderit.

4. Quamdiu corpora gravia a n.o.bis sustinentur, sentimus in n.o.bismet ipsis nisum, fatigationem, et molestiam. Percipimus etiam in gravibus cadentibus motum acceleratum versus centrum telluris; ope sensuum praeterea nihil.

Ratione tamen colligitur causam esse aliquam vel principium horum phaenomenon; illud autem _gravitas_ vulgo nuncupatur. Quoniam vero causa descensus gravium caeca sit et incognita, gravitas ea acceptione proprie dici nequit qualitas sensibilis; est igitur qualitas occulta. Sed vix, et ne vix quidem, concipere licet quid sit qualitas occulta, aut qua ratione qualitas ulla agere aut operari quidquam possit. Melius itaque foret, si, missa qualitate occulta, homines attenderent solummodo ad effectus sensibiles; vocibusque abstractis (quantumvis illae ad disserendum utiles sint) in meditatione omissis, mens in particularibus et concretis, hoc est in ipsis rebus, defigeretur.

5. _Vis_(929) similiter corporibus tribuitur: usurpatur autem vocabulum illud, tanquam significaret qualitatem cognitam, distinctamque tarn a motu, figura, omnique alia re sensibili, quam ab omni animalis affectione: id vero nihil aliud esse quam qualitatem _occultam_, rem acrius rimanti constabit. Nisus animalis et motus corporeus vulgo spectantur tanquam symptomata et mensurae hujus qualitatis occultae.

6. Patet igitur gravitatem aut vim frustra poni pro principio(930) motus: nunquid enim principium illud clarius cognosci potest ex eo quod dicatur qualitas occulta? Quod ipsum occultum est, nihil explicat: ut omittamus causam agentem incognitam rectius dici posse substantiam quam qualitatem.

Porro _vis_, _gravitas_, et istiusmodi voces, saepius, nec inepte, in concreto usurpantur; ita ut connotent corpus motum, difficultatem resistendi, &c. Ubi vero a philosophis adhibentur ad significandas naturas quasdam, ab hisce omnibus praecisas et abstractas, quae nec sensibus subjiciuntur, nec ulla mentis vi intelligi nec imaginatione effingi(931) possunt, turn demum errores et confusionem pariunt.

7. Multos autem in errorem ducit, quod voces generales et abstractas in disserendo utiles esse videant, nec tamen earum vim satis capiant. Partim vero a consuetudine vulgari inventae sunt illae ad sermonem abbreviandum, partim a philosophis ad docendum excogitatae; non quod ad naturas rerum accommodatas sint, quae quidem singulares et concretae existunt; sed quod idoneae ad tradendas disciplinas, propterea quod faciant notiones, vel saltem propositiones, universales(932).

8. _Vim corpoream_ esse aliquid conceptu facile plerumque existimamus. Ii tamen qui rem accuratius inspexerunt in diversa sunt opinione; uti apparet ex mira verborum obscuritate qua laborant, ubi illam explicare conantur.

Torricellius ait vim et impetum esse res quasdam abstractas subtilesque et quintessentias, quae includuntur in substantia corporea, tanquam in vase magico Circes(933). Leibnitius item in naturae vi explicanda haec habet-_Vis activa, primitiva, quae est ??te???e?a p??t?, animae vel formae substantiali __ respondet_. Vide _Acta Erudit. Lips._ Usque adeo necesse est ut vel summi viri, quamdiu abstractionibus indulgent, voces nulla certa significatione praeditas, et meras scholasticorum umbras sectentur. Alia ex neotericorum scriptis, nec pauca quidem ea, producere liceret; quibus abunde constaret, metaphysicas abstractiones non usquequaque cessisse mechanicae et experimentis, sed negotium inane philosophis etiamnum facessere.

9. Ex illo fonte derivantur varia absurda, cujus generis est illud, _vim percussionis, utcunque exiguae, esse infinite magnam_. Quod sane supponit, gravitatem esse qualitatem quandam realem ab aliis omnibus diversam; et gravitationem esse quasi actum hujus qualitatis, a motu realiter distinctum: minima autem percussio producit effectum majorem quam maxima gravitatio sine motu; ilia scilicet motum aliquem edit, haec nullum. Unde sequitur, vim percussionis ratione infinita excedere vim gravitationis, hoc est, esse infinite magnam(934). Videantur experimenta Galilaei, et quae de definita vi percussionis scripserunt Torricellius, Borellus, et alii.

10. Veruntamen fatendum est vim nullam per se immediate sentiri; neque aliter quam per effectum(935) cognosci et mensurari. Sed vis mortuae, seu gravitationis simplicis, in corpore quiescente subjecto, nulla facta mutatione, effectus nullus est; percussionis autem, effectus aliquis.

Quoniam, ergo, vires sunt effectibus proportionales, concludere licet vim mortuam(936) esse nullam. Neque tamen propterea vim percussionis esse infinitam: non enim oportet quant.i.tatem ullam positivam habere pro infinita, propterea quod ratione infinita superet quant.i.tatem nullam sive nihil.

11. Vis gravitationis a momento secerni nequit; momentum autem sine celeritate nullum est, quum sit moles in celeritatem ducta: porro celeritas sine motu intelligi non potest; ergo nec vis gravitationis.

Deinde vis nulla nisi per actionem innotescit, et per eandem mensuratur; actionem autem corporis a motu praescindere non possumus; ergo quamdiu corpus grave plumbi subjecti vel chordae figuram mutat, tamdiu movetur; ubi vero quiescit, nihil agit, vel, quod idem est, agere prohibetur. Breviter, voces istae _vis mortua_ et _gravitatio_, etsi per abstractionem metaphysicam aliquid significare supponuntur diversum a movente, moto, motu et quiete, revera tamen id totum nihil est.

12. Siquis diceret pondus appensum vel impositum agere in chordam, quoniam impedit quominus se rest.i.tuat vi elastica: dico, pari ratione corpus quodvis inferum agere in superius inc.u.mbens, quoniam illud descendere prohibet: dici vero non potest actio corporis, quod prohibeat aliud corpus existere in eo loco quern occupat.

13. Pressionem corporis gravitantis quandoque sentimus. Verum sensio ista molesta oritur ex motu corporis istius gravis fibris nervisque nostri corporis communicato, et eorundem situm immutante; adeoque percussioni accepta referri debet. In hisce rebus multis et gravibus praejudiciis laboramus, sed illa acri atque iterata meditatione subigenda sunt(937), vel potius penitus averruncanda.

14. Quo probetur quant.i.tatem ullam esse infinitam, ostendi oportet partem aliquam finitam h.o.m.ogeneam in ea infinities contineri. Sed vis mortua se habet ad vim percussionis, non ut pars ad totum, sed ut punctum ad lineam, juxta ipsos vis infinitae percussionis auctores. Multa in hanc rem adjicere liceret, sed vereor ne prolixus sim.

15. Ex principiis praemissis lites insignes solvi possunt, quae viros doctos multum exercuerunt. Hujus rei exemplum sit controversia illa de proportione virium. Una pars dum concedit, momenta, motus, impetus, data mole, esse simpliciter ut velocitates, affirmat vires esse ut quadrata velocitatum. Hanc autem sententiam supponere vim corporis distingui(938) a momento, motu, et impetu; eaque suppositione sublata corruere, nemo non videt.

16. Quo clarius adhuc appareat, confusionem quandam miram per abstractiones metaphysicas in doctrinam de motu introductam esse, videamus quantum intersit inter notiones virorum celebrium de vi et impetu.

Leibnitius impetum c.u.m motu confundit. Juxta Newtonum(939) impetus revera idem est c.u.m vi inertiae. Borellus(940) a.s.serit impetum non aliud esse quam gradum velocitatis. Alii impetum et conatum inter se differre, alii non differre volunt. Plerique vim motricem motui proportionalem intelligunt.

Nonnulli aliam aliquam vim praeter motricem, et diversimode mensurandam, utpote per quadrata velocitatum in moles, intelligere _prae_ se ferunt. Sed infinitum esset haec prosequi.

17. _Vis_, _gravitas_, _attractio_, et hujusmodi voces, utiles(941) sunt ad ratiocinia et computationes de motu et corporibus motis; sed non ad intelligendam simplicem ipsius motus naturam, vel ad qualitates totidem distinctas designandas. Attractionem certe quod attinet, patet illam ab Newtono adhiberi, non tanquam qualitatem veram et physicam, sed solummodo ut hypothesin mathematicam(942). Quinetiam Leibnitius, nisum elementarem seu solicitationem ab impetu distinguens, fatetur illa entia non re ipsa inveniri in rerum natura, sed abstractione facienda esse.

18. Similis ratio est compositionis et resolutionis virium quarumcunque directarum in quascunque obliquas, per diagonalem et latera parallelogrammi. Haec mechanicae et computationi inserviunt: sed aliud est computationi et demonstrationibus mathematicis inservire, aliud rerum naturam exhibere.

19. Ex recentioribus multi sunt in ea opinione, ut putent motum neque destrui nec de novo gigni, sed eandem(943) semper motus quant.i.tatem permanere. Aristoteles etiam dubium illud olim proposuit-utrum motus factus sit et corruptus, an vero ab aeterno? _Phys._ lib. viii. Quod vero motus sensibilis pereat, patet sensibus: illi autem eundem impetum, nisum, aut summam virium eandem manere velle videntur. Unde affirmat Borellus, vim in percussione non imminui, sed expandi; impetus etiam contrarios suscipi et retineri in eodem corpore. Item Leibnitius nisum ubique et semper esse in materia, et ubi non patet sensibus, ratione intelligi contendit.-Haec autem nimis abstracta esse et obscura, ejusdemque fere generis c.u.m formis substantialibus et entelechiis, fatendum.

20. Quotquot ad explicandam motus causam atque originem, vel principio hylarchico, vel naturae indigentia, vel appet.i.tu, aut denique instinctu naturali utuntur, dixisse aliquid potius quam cogita.s.se censendi sunt.

Neque ab hisce multum absunt qui supposuerint(944) _partes terrae esse se moventes, aut etiam spiritus iis implantatos ad instar formae_, ut a.s.signent causam accelerationis gravium cadentium: aut qui dixerit(945), _in corpore praeter solidam extensionem debere etiam poni aliquid unde virium consideratio oriatur_. Siquidem hi omnes vel nihil particulare et determinatum enuntiant; vel, si quid sit, tarn difficile erit illud explicare, quam id ipsum cujus explicandi causa adducitur(946).

21. Frustra ad naturam ill.u.s.trandam adhibentur ea quae nec sensibus patent, nec ratione intelligi possunt. Videndum ergo quid sensus, quid experientia, quid demum ratio iis innixa, suadeat. Duo sunt summa rerum genera-_corpus_ et _anima_. Rem extensam, solidam, mobilem, figuratam, aliisque qualitatibus quae sensibus occurrunt praeditam, ope sensuum; rem vero sentientem, percipientem, intelligentem, conscientia quadam interna cognovimus. Porro, res istas plane inter se diversas esse, longeque heterogeneas, cernimus. Loquor autem de rebus cognitis: de incognitis enim disserere nil juvat(947).

22. Totum id quod novimus, cui nomen _corpus_ indidimus, nihil _in se_ continet quod motus principium seu causa efficiens esse possit. Etenim impenetrabilitas, extensio, figura nullam includunt vel connotant potentiam producendi motum; quinimo e contrario non modo illas, verum etiam alias, quotquot sint, corporis qualitates sigillatim percurrentes, videbimus omnes esse revera pa.s.sivas, nihilque iis activum inesse, quod ullo modo intelligi possit tanquam fons et principium motus(948).

Gravitatem quod attinet, voce illa nihil cognitum et ab ipso effectu sensibili, cujus causa quaeritur, diversum significari jam ante ostendimus.

Et sane quando corpus grave dicimus, nihil aliud intelligimus, nisi quod feratur deorsum; de causa hujus effectus sensibilis nihil omnino cogitantes.

23. De corpore itaque audacter p.r.o.nunciare licet, utpote de re comperta, quod non sit principium motus. Quod si quisquam, praeter solidam extensionem ejusque modificationes, vocem _corpus_ qualitatem etiam _occultam_, virtutem, formam, essentiam complecti sua significatione contendat; licet quidem illi inutili negotio sine ideis disputare, et nominibus nihil distincte exprimentibus abuti. Caeterum sanior philosophandi ratio videtur ab notionibus abstractis et generalibus (si modo notiones dici debent quae intelligi nequeunt) quantum fieri potest abstinuisse.

24. Quicquid continetur in idea corporis novimus; quod vero novimus in corpore, id non esse principium motus constat(949). Qui praeterea aliquid incognitum in corpore, cujus ideam nullam habent, comminisc.u.n.tur, quod motus principium dicant, ii revera nihil aliud quam _principium motus esse incognitum_ dic.u.n.t. Sed hujusmodi subtilitatibus diutius immorari piget.

25. Praeter res corporeas alterum est _genus rerum cogitantium_(950). In iis autem potentiam inesse corpora movendi, propria experientia didicimus(951); quandoquidem anima nostra pro lubitu possit ciere et sistere membrorum motus, quacunque tandem ratione id fiat. Hoc certe constat, corpora moveri ad nutum animae; eamque proinde haud inepte dici posse principium motus: particulare quidem et subordinatum, quodque ipsum dependeat a primo et universali Principio(952).

26. Corpora gravia feruntur deorsum, etsi nullo impulsu apparente agitata; non tamen existimandum propterea in iis contineri principium motus: cujus rei hanc rationem a.s.signat Aristoteles(953);-_Gravia et levia_ (inquit) _non moventur a seipsis; id enim vitale esset, et se sistere possent_.

Gravia omnia una eademque certa et constanti lege centrum telluris petunt, neque in ipsis animadvert.i.tur principium vel facultas ulla motum istum sistendi, minuendi, vel, nisi pro rata proportione, augendi, aut denique ullo modo immutandi: habent adeo se pa.s.sive. Porro idem, stricte et accurate loquendo, dicendum de corporibus percussivis. Corpora ista quamdiu moventur, ut et in ipso percussionis momento, si gerunt pa.s.sive, perinde scilicet atque c.u.m quiesc.u.n.t. Corpus iners tam agit quam corpus motum, si res ad verum exigatur: id quod agnoscit Newtonus, ubi ait, vim inertiae esse eandem c.u.m impetu(954). Corpus autem iners et quietum nihil agit, ergo nee motum.

27. Revera corpus aeque perseverat in utrovis statu, vel motus vel quietis.

Ista vero perseverantia non magis dicenda est actio corporis, quam existentia ejusdem actio diceretur. Perseverantia nihil aliud est quam continuatio in eodem modo existendi, quae proprie dici actio non potest.

Caeterum resistentiam, quam experimur in sistendo corpore moto, ejus actionem esse fingimus vana specie delusi. Revera enim ista resistentia quam sentimus(955), pa.s.sio est in n.o.bis, neque arguit corpus agere, sed nos pati: constat utique nos idem pa.s.suros fuisse, sive corpus illud a se moveatur, sive ab alio principio impellatur.

28. Actio et reactio dic.u.n.tur esse in corporibus: nec incommode ad demonstrationes mechanicas(956). Sed cavendum, ne propterea supponamus virtutem aliquam realem, quae motus causa sive principium sit, esse in iis.