imagine the _physical force_ that is supposed to inhabit bodies, and to
explain their motions. The conception of motion has been the parent of
innumerable paradoxes and seeming contradictions among ancient Greek
thinkers; for it presents, in a striking form, the metaphysical
difficulties in the way of a reconciliation of the One and the
Many—difficulties which Berkeley had already attributed to perverse
abstractions, with which philosophers amused themselves and blocked up the
way to concrete knowledge; first wantonly raising a dust, and then
complaining that they could not see. Nor has modern mechanical science in
this respect fared better than the old philosophies. Even its leaders,
Torricelli, for instance, and Leibniz, offer us scholastic shadows—empty
metaphysical abstractions—when they speak about an active power that is
supposed to be lodged within the things of sense. Torricelli tells us that
the forces within the things around us, and within our own bodies, are
“subtle quintessences, enclosed in a corporeal substance as in the
enchanted vase of Circe”; and Leibniz speaks of their active powers as
their “substantial form,” whatever that can be conceived to mean. Others
call the power to which change of place is due, the hylarchic principle,
an appetite in bodies, a spontaneity inherent in them; or they assume
that, besides their extension, solidity, and other qualities which appear
in sense, there is also something named force, latent in them if not
patent—in all which we have a flood of words, empty of concrete thought.
At best the language is metaphorical (sect. 2-9).
For showing the active cause at work in the production of motion in
bodies, it is of no avail to name, as if it were a datum of sense, what is
not presentable to our senses. Let us, instead, turn to the only other
sort of data in realised experience. For we find only two sorts of
realities in experience, the one sort revealed by our senses, the other by
inward consciousness. We can affirm nothing about the contents of _bodies_
except what our senses present, namely, concrete things, extended,
figured, solid, having also innumerable other qualities, which seem all to
depend upon change of place in the things, or in their constituent
particles. The contents of _mind_ or _spirit_, on the other hand, are
disclosed to inner consciousness, which reveals a sentient Ego that is
actively percipient and exertive. And it must be in the second of these
two concrete revelations of reality, that active causation, on which
motion and all other change depends, is to be found—not in empty
abstractions, covered by words like _power_, _cause_, _force_, or _nisus_,
which correspond to nothing perceived by the senses (sect. 21).
So that which we call body presents _within itself_ nothing in which
change of place or state can originate causally. Extension, figure,
solidity, and all the other perceptible constituents of bodies are
appearances only—passive phenomena, which succeed one another in an
orderly cosmical procession, on which doubtless our pains and pleasures
largely depend. But there is no sensibly perceptible power found among
those sensuous appearances. They can only be _caused causes_, adapted, as
we presuppose, to signify to us what we may expect to follow that
appearance. The reason of their significance, i.e. of the constancy of
their sequences and coexistences, must be sought for _outside of
themselves_. Experimental research may discover new terms among the
correlated cosmical sequences or coexistences, but the newly discovered
terms must still be only passive phenomena previously unperceived. Body
means only what is presentable to the senses. Those who attribute to it
something not perceptible by sense, which they call the force or power in
which its motions originate, say in other words that the origin of motion
is unknowable by sense (sect. 22-24).
Turn now from things of sense, the data of perception, to Mind or Spirit,
as revealed in inner consciousness. Here we have a deeper and more real
revelation of what underlies, or is presupposed in, the passive cosmical
procession that is presented to the senses. Our inward consciousness
plainly shews the thinking being actually _exercising_ power to move its
animated body. We find that we can, by a causal exertion of which we are
distinctly conscious, either excite or arrest movements in bodies. In
voluntary exertion we have thus a concrete example of force or power,
_producing_ and not merely _followed by_ motion. In the case of human
volition this is no doubt conditioned power; nevertheless it exemplifies
Power on a greater scale than human, even Divine power, universally and
continuously operative, in all natural motions, and in the cosmical laws
according to which they proceed (sect. 25-30).
Thus those who pretend to find force or active causation _within_ bodies,
pretend to find what their sensuous experience does not support, and they
have to sustain their pretence by unintelligible language. On the other
hand, those who explain motion by referring it to conscious exertion of
personal agents, say what is supported by their own consciousness, and
confirmed by high authorities, including Anaxagoras, Plato, Aristotle,
Descartes, and Newton, demonstrating that in Spirit only do we find power
to change its own state, as well as the states and mutual relations of
bodies. Motion in nature is God continuously acting (sect. 31-34). But
physical science is conveniently confined to the order of the passive
procession of sensuous appearances, including experiments in quest of the
rules naturally exemplified in the motions of bodies: reasoning on
mathematical and mechanical principles, it leaves the contemplation of
active causation to a more exalted science (sect. 35-42).
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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 passive, 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 pronounced good or
evil on account of acts of will that are not mere caused causes—passively
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 God?
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While the principle of Causation, in its application to change of place on
the part of bodies and their constituent 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 assumes 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 passive: 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 assumed, 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
space contained only one solitary body: a plurality of bodies is
indispensable to its appearance. Absolute motion of a solitary body, in
otherwise absolutely empty space, is an unmeaning abstraction, a
collocation of empty words. This leads into an inquiry about relative
space as well as relative place, and the intelligibility of absolute
space, place, and motion (sect. 52-64).
Local motion is unintelligible unless we understand the meaning of
_space_. Now some philosophers distinguish between absolute space, which
with them is ultimately the only real space, 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 space 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 space, 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 space which a body occupies
as part of a space that is necessarily abstracted from all sentient
experience; nor of real motion as change within absolute space, 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).
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Finally, is motion, thus explained, something that can be spoken of as an
entity communicable from one body to another body? May we think of it as a
datum of sense existing in the striking body, and then passing 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 Identity 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 passes
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 præcipuum est cavisse ne voces males
intellectæ(925) nobis officiant: quod omnes fere monent philosophi, pauci
observant. Quanquam id quidem haud adeo difficile videtur, in rebus
præsertim physicis tractandis, ubi locum habent sensus, experientia, et
ratiocinium geometricum. Seposito igitur, quantum licet, omni præjudicio,
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.
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2. Motus contemplatio mire torsit veterum philosophorum(926) mentes, unde
natæ sunt variæ opiniones supra modem difficiles, ne dicam absurdæ; quæ,
quum jam fere in desuetudinem abierint, haud merentur ut iis discutiendis
nimio studio immoremur. Apud recentiores autem et saniores hujus ævi
philosophos(927), ubi de Motu agitur, vocabula haud pauca abstractæ nimium
et obscuræ significationis occurrunt, cujusmodi sunt _solicitatio
gravitatis_, _conatus_, _vires mortuæ_, &c., quæ scriptis, alioqui
doctissimis, tenebras offundunt, sententiisque non minus a vero, quam a
sensu hominum communi abhorrentibus, ortum præbent. Hæc vero necesse est
ut, veritatis gratia, non alios refellendi studio, accurate discutiantur.
3. _Solicitatio_ et _nisus_, sive _conatus_, rebus solummodo animatis
revera competunt(928). Cum aliis rebus tribuuntur, sensu metaphorico
accipiantur necesse est. A metaphoris autem abstinendum philosopho. Porro,
seclusa omni tarn animæ affectione quam corporis motione, nihil clari ac
distincti iis vocibus significari, cuilibet constabit qui modo rem serio
perpenderit.
4. Quamdiu corpora gravia a nobis sustinentur, sentimus in nobismet ipsis
nisum, fatigationem, et molestiam. Percipimus etiam in gravibus cadentibus
motum acceleratum versus centrum telluris; ope sensuum præterea nihil.
Ratione tamen colligitur causam esse aliquam vel principium horum
phænomenon; illud autem _gravitas_ vulgo nuncupatur. Quoniam vero causa
descensus gravium cæca 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 illæ 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 mensuræ hujus qualitatis occultæ.
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, sæpius, 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 præcisas et abstractas, quæ 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 inventæ sunt illæ ad sermonem abbreviandum,
partim a philosophis ad docendum excogitatæ; non quod ad naturas rerum
accommodatas sint, quæ quidem singulares et concretæ existunt; sed quod
idoneæ 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, quæ includuntur in substantia corporea, tanquam in vase
magico Circes(933). Leibnitius item in naturæ vi explicanda hæc habet—_Vis
activa, primitiva, quæ est ἐντελέχεια πρώτη, animæ vel formæ substantiali
__ respondet_. Vide _Acta Erudit. Lips._ Usque adeo necesse est ut vel
summi viri, quamdiu abstractionibus indulgent, voces nulla certa
significatione præditas, et meras scholasticorum umbras sectentur. Alia ex
neotericorum scriptis, nec pauca quidem ea, producere liceret; quibus
abunde constaret, metaphysicas abstractiones non usquequaque cessisse
mechanicæ et experimentis, sed negotium inane philosophis etiamnum
facessere.
9. Ex illo fonte derivantur varia absurda, cujus generis est illud, _vim
percussionis, utcunque exiguæ, 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, hæc nullum. Unde
sequitur, vim percussionis ratione infinita excedere vim gravitationis,
hoc est, esse infinite magnam(934). Videantur experimenta Galilæi, et quæ
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 mortuæ, 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 quantitatem ullam positivam habere pro
infinita, propterea quod ratione infinita superet quantitatem 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 præscindere non possumus; ergo quamdiu
corpus grave plumbi subjecti vel chordæ figuram mutat, tamdiu movetur; ubi
vero quiescit, nihil agit, vel, quod idem est, agere prohibetur. Breviter,
voces istæ _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 restituat vi elastica: dico, pari ratione corpus
quodvis inferum agere in superius incumbens, 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 præjudiciis
laboramus, sed illa acri atque iterata meditatione subigenda sunt(937),
vel potius penitus averruncanda.
14. Quo probetur quantitatem ullam esse infinitam, ostendi oportet partem
aliquam finitam homogeneam 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 infinitæ percussionis auctores. Multa in hanc rem adjicere
liceret, sed vereor ne prolixus sim.
15. Ex principiis præmissis lites insignes solvi possunt, quæ 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.