49
Metafísica y Persona. Filosofía, conocimiento y vida
Año 15, Núm. 30, Julio-Diciembre, 2023, ISSN: 2007-9699
Some remarks on Leibniz’s criticisms to mechanics
Algunas observaciones sobre las críticas de Leibniz a la mecánica
UPAEP, Universidad
roberto.casales@upaep.mx
The main purpose of this paper is to analyze some of Leibniz’s critics of mechanics in
order to understand its limitations, particularly those that help to clarify the distinction
between the machines made by human beings and machines of nature. To understand
Leibniz’s critics of mechanics, we divided them into three kinds: 1. critics of the Cartesian
conception of extension; 2. Leibniz´s mill argument; and 3. the irreducibility of living be-
ing too simple machines or artifacts.
Keywords: force, mechanics, machine of nature, perception, body.
El objetivo principal de este artículo es analizar algunas de las críticas de Leibniz al
mecanicismo, con la intención de comprender sus limitaciones, particularmente aquellas
que nos ayudan a esclarecer la distinción entre las máquinas fabricadas por los seres hu-
manos y las máquinas de la naturaleza. Para entender las críticas de Leibniz al mecanicis-
mo, las hemos dividido en tres: 1. las críticas a la concepción cartesiana de extensión; 2.
el argumento leibniziano del molino; y 3. la irreductibilidad de los seres vivos a simples
máquinas o artefactos.
Palabras clave: fuerza, mecanicismo, máquina de la naturaleza, percepción, cuerpo.
Introduction
In a famous letter to Nicolas Remond, dated on January 10
th
of 1714,
Leibniz mentioned that, after studying some modern philosophers and
1
Metafísica y persona. Filosofía, conocimiento y vida
Año 15, Núm. 30, Julio-Diciembre, 2023, ISSN: 2007-9699
50
thinkers at the age of fifteen, he went to the Rosetal to deliberate whether
to preserve substantial forms or not. Even when he chooses mechanics
over metaphysics at that moment, his further investigations on the ulti-
mate grounds of mechanics and the laws of motion lead him to conclude
2
A statement that can also be found in his New
System of the Nature and the Communication of Substances of 1695, where he
argues that
after trying to explore the principles of mechanics itself in order to account
for the laws of nature which we learn from experience, I perceived that the
sole consideration of extended mass was not enough but that it was necessary,
in addition, to use the concept of force […] althought it falls within the sphere
of metaphysics.
3
These biographical notes let us see that his adscription to mechanics was
ambiguous since he, on one side, state that every natural phenomena could
-
cally, since they depend on more sublime principles which show the wisdom
4
Even when Leibniz is considered as a relevant precursor for computing
5
especially for his improvements in mathemat-
ics and logic, his developments for the mines of Harz, and his calculator,
his ambiguous adscription to mechanics reveals some of the limits not only
of this account of nature but also of our technological improvements. The
main purpose of this paper is to analyze some of Leibniz’s critics of me-
chanics in order to understand these limitations, particularly those that
help to clarify the distinction between the machines made by human beings
and machines of nature. To understand Leibniz’s critics of mechanics, we
divided these into three kinds: 1. critics of the Cartesian conception of ex-
tension; 2. Leibniz´s mill argument; and 3. the irreducibility of living being
too simple machines or artifacts.
2
Loemker, 655. All references from Leibniz and Descartes will be quoted according to the
canonical style of citation.
3
Loemker, 454; GP IV, 478.
4
Tentamen anagogicum, Loemecker, 478; GP VII, 272; see also: Extrait d’une leer de M. de Leibniz
sur la question, si l’essence du corps consiste dans l’Etendue, Lamarra 204-205.
5
, A., Leibniz. Máquinas inteligentes, multicultura-
lismo y ética de la vida, Granada: Comares (Nova Leibniz Latina 2), pp. 5-28.
51
Some remarks about Leibniz’s critics to mechanics
The insuciency of the Cartesian conception of extension
Descartes notion of extension is quite relevant for mechanics not only be-
cause he sustains that extension constitutes the true nature or essence of all
bodies,
6
but also because, as Gilson noticed, it allows him to develop a form of
7
If the essence of all
bodies consists in extension, then we can measure and describe every natural
phenomena through the lengths of a mathematical equation. Even when Leib-
niz accepts that every natural phenomena can be explained mechanically, and
thus by mathematical means, he clearly sustain in a brief text of 1677 that this
account of nature only correspond to our cognitive limitations:
First of all, I take it to be certain that all things come about through certain
intelligible causes, or causes which we could perceive if some angel wished
to reveal them to us. And since we may perceive nothing accurately except
to be explained through these four. But because we are now speaking of those
things which seem to take place without perception, such as the reactions of
liquids, the precipitations of salts, etc., we have no means of explaining them
8
According to Leibniz, extension and mechanics only correspond to how
we can represent the external and phenomenical world through perception:
every natural phenomena can be explained mechanically, through mathe-
matical means, only because, as we can see in his correspondence with De
in things, like the rainbow or the mock-sun, and all reality belongs only to
9
By giving a phenomenical character to all bodies, Leibniz is not
saying that they lack of reality, but only that it is grounded in something
else and, therefore, that the true essence or nature of bodies cannot consist
only in extension. What Leibniz is denying is the substantial character of ex-
-
into plurality, continuity and coexistence or the existence of parts at one and
10
As a property of things, according to Leibniz, extension is
6
Treatise on light, Ariew 37; AT XI, 36.
7
The Unity of Philosophical Experience, New York: Charles Scribner’s Sons, 1950, p. 133.
8
De modo perveniendi ad veram corporum analysin et resum naturalium causas, Loemker,
173; GP VII, 265.
9
Leer from Leibniz to De Volder from June 30th of 1704, Loemker, 536; GP II, 270.
10
Leer from Leibniz to De Volder from march 24
th
of 1699, Loemker, 516; GP II, 169.
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11
In a second argument to deny the substantiality of extension, as we can see
in a brief text from 1691, Leibniz state that if the true essence of bodies consists
in extension, extension alone should be enough to explain every property of
bodies.
12
Extension, as Laura Herrera noticed,
13
is not enough to explain the
transmission of movement that happens in the collision of two or more bodies,
would be, at most, explained by the mere geometric composition of move-
ments, without explaining the ultimate causes of movement.
14
Another reason
-
cannot make up a complete entity, no action or change can be deduced from it,
it expresses only a present state, not at all the future and past as the concept of a
15
16
Both reasons to deny the substantial character of extension aim to the
-
plies that if we need to
change the point of view from foronomics to dynamics. Alternatively, if de-
sired, to pass from describing movement with exactitude to explain it. The
distinction between describing and explaining seem unequivocal, as it can
be seen when we confront rough descriptions and explanations that lead us
to the ultimate causes.
17
Even when we can explain everything mechanically, mechanics only rep-
resents one form to approach to nature, especially when we want to under-
stand the realm of living beings, as we will see in Leibniz’s mill argument
against mechanical materialism.
11
Nullum quidem librum contra philosohpian Cartesianam
12
Extrait d’une leer de M. de Leibniz sur la question, si l’essence du corps consiste dans l’Etendue,
Lamarra, 203.
13
, S. &
, M. (Eds.), Leibniz en la losofía y la ciencia modernas, Granada: Comares,
2010, p. 284.
14
Extrait d’une leer de M. de Leibniz sur la question, si l’essence du corps consiste dans l’Etendue,
Lamarra, 203.
15
Draft of a leer from Leibniz to Arnauld, Mason, 88; Finster, 186.
16
Draft of ‘New System for the Explaining the Nature of Substances and the Communication between
them, as well as the Union of the Soul with the Body, Woolhouse, 25; GP IV, 476.
17
Juan Arana 2013: 63.
53
Some remarks about Leibniz’s critics to mechanics
Leibniz’s mill argument against mechanical materialism
Beyond the Cartesian conception of extension and its applications to nat-
measured and, therefore, described through a mathematical equation, but
also that we can explain every single natural change by understanding two
things: the parts that constitute the machine, i.e., the gears that make this ma-
chine work, and the way that these parts interact.
18
Leibniz believes that we
can only apply this mechanical criterion to explain the interaction of bodies,
19
since bodies, according to §79 of his Monadology,
20
Howev-
er, he also states that we cannot apply the same criterion to explain the inner
21
since their
inner actions, as he states in §2 of his Principles of Nature and of Grace, Based on
Reasonperceptions –that is to say, the representations of the
compound, or of that which is without, in the simple– and its appetitions –that
is to say, its tendencies from one perception to another– which are the prin-
22
By grounding mechanics in his dynamics and not only in
-
New Essays in Human Understanding
23
or, as he claims in the §1 of his Principles of Nature and of Grace,
Based on Reasonsubstance
24
while in bodies or
compounds their activity consist in motion, the activity of monads consist in
perception and appetite, two inner activities of this soul-like entities.
When Leibniz state that each body or compound is not one substance but
an aggregate of substances,
25
he is also saying that the force that explains mo-
tion, considered as a derivative force, proceeds from an inner primitive force
26
According to this approach, as we can see
18
, H., ¿Qué es la naturaleza? Introducción losóca a la historia de la
ciencia, México: Porrúa, 2007, p. 87.
19
Considerations on vital Principles and Plastic Natures, Loemker, 587; GP VI, 541.
20
Loemker, 651; GP VI, 620.
21
Monadology, Loemker, 643; GP VI, 607.
22
Loemker, 636; Robinet I, 29.
23
AA VI, 6, 53.
24
Loemker, 636; Robinet I, 27.
25
Communicata ex disputationibus cum Fardella, de serie rerum, corporibus et substantiis, et de praede-
terminatione, AA VI, 4B, 1668.
26
Leer from Leibniz to De Volder from June 20th of 1703, Loemker, 530; GP II, 251.
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in §11 of his On Nature Itself-
force of resistance that he locates in prime maer-
27
Since action and motion
are not something that can be derived from this prime maer or mass, Leibniz
concludes that we need to presuppose something else in bodies that explain
-
stance a primary entelechyprôton dektikòn) of activity, that is,
a primitive motive force which, superadded to extension, or what is merely
geometrical, and mass, or what is merely material, always acts indeed and
28
As we can see
in §11 of his New System, these primary entelechies constitute the
real unities absolutely devoid of parts, that can be the sources of actions, and
ultimate elements in the analysis of sunstances…they have something of the
nature of life and a kind of perception.
29
Even when we can explain every corporal movement by mechanical means,
as the result of the impact of another body, this movement can be described,
in Leibniz’s opinion, as an external expression of the inner force of things,
something that depends on the existence of monads. This soul-like entities,
internal principle
30
The inner action of
monads, as we already state, consist in perception and appetite: while per-
etail in that which changes
31
which
express or represent what is outside (the external world) from the inside,
32
as
33
Since monads are
always acting, we can infer that they are always perceiving and passing from
one perception to another, even when they are not aware of their own per-
ceptions, as we can see in the Preface of his New Essays, when he introduced
-
soul itself, of which we are unaware because these impressions are either too
27
Loemker, 503; GP IV, 510.
28
On Nature Itself, Loemker, 503; GP IV, 511.
29
Woolhouse, 16; GP IV, 482-483.
30
Monadology, Loemker, 643-644; GP VI, 608.
31
Monadology, Loemker, 644; GP VI, 608.
32
Leer to R.C. Wagner from June 4th of 1710, GP VII, 329-330.
33
Monadology, Loemker, 644; GP VI, 609.
55
Some remarks about Leibniz’s critics to mechanics
-
34
Monads always perceive something, even
those monads whose perceptions cannot reach the level of sensation.
35
All of
this allow us to understand the ontological background of his mill argument
against mechanical materialism, as we can see in §17 of his Monadology:
It must be confessed, moreover, that perception and what depends on it are
inexplicable by mechanical reasons-
tend that there is a machine whose structure enables it to think, feel, and
have perception, one could think of it as enlarged yet preserving its same
proportions, so that one could enter it as one does a mill. If we did this, we
never see anything which would explain a perception. So it is in the simple
substance, and not in the composite substance or machine, that perception
must be sought. Furthermore, this is the only thing –namely, perceptions
and their changes- that can be found in simple substance. It is in this alone
that the internal actions of simple substances can consist.
36
As Paul Lodge noticed, the key to understand Leibniz’s mill argument is
-
poreal being is a mechanical system and, therefore, that material things are
entities whose behavior can be accurately and exhaustively explained by ad-
verting to nothing other than the sizes and shapes of impenetrable particles
that have the power to receive motion from other particles through impact or
as a result of the direct activity of immaterial entities upon them.
37
will see that Leibniz agrees with mechanical materialists in saying that every
corporeal natural phenomenon is prone to a mechanical explanation, some-
thing that, however, cannot apply to perception and appetite, the inner ac-
tivity of monads, since they do not depend on any corporeal or geometrical
thing. Mental states like perception and appetite, even when they could be
related with sensation and, in this way, with the impressions that we receive
through some of our organs, cannot be explained in mechanical terms since
38
By understanding
the parts that constitute our body, conceived as a natural machine, and the
34
AA VI, 6, 53.
35
Monadology, Loemker, 644; GP VI, 610.
36
Monadology, Loemker, 644; GP VI, 609.
37
Ergo, vol. 1,
num. 3, 2014, p. 81.
38
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way they interact, i.e., the way that they behave, we would never see some-
thing that explains our mental states:
sentient or thinking being is not a mechanical thing like a watch or a mill: one
cannot conceive of sizes and shapes and motions combining mechanically to
produce something which thinks, and senses too, in a mass where [formerly]
there was nothing of the kind.
39
Machines of nature vs artifacts
As we can see at the end of §2 of his New System, Leibniz’s concerns about
mechanics are not only related to the Cartesian notion of extension but also
-
40
Leibniz also makes this critic to Descartes when he explains, in
§2 of his Principles of Nature and of Grace, Based on Reason, the distinction be-
stating that all our perceptions are apperceived, i.e., that every mental state
is conscious,
41
that there is no soul in beast, still less other principles of life
42
In this way,
Leibniz not only recognize that animals have souls but also that every living
being have one, including plants, since they have perceptions and appetites:
43
All of
this means that even when Leibniz accepts a mechanical account of bodies,
44
The reason
not only that living beings have a soul that guarantees the unity of the entire
organism, since bodies without a soul can only be considered as mere aggre-
gates of beings without any further vinculum
45
–while living beings are still
-
39
New Essays, AA VI, 6, 66-67.
40
Woolhouse, 11; GP IV, 478.
41
AT, VIII, 160.
42
Loemker, 637; Robinet I, 37.
43
New Essays, AA VI, 6, 139.
44
Machines of Nature and
Corporeal Substances in Leibniz, Dordrecht-Heidelberg-London-New York: Springer, 2011, p. 65.
45
Nullum quidem librum contra philosohpian Cartesianam, GP IV, 395-396.
57
Some remarks about Leibniz’s critics to mechanics
cations–,
46
but also because their complex structure, which make them quite
Monadology:
So each organic body belonging to a living being is a kind of divine machine
-
chine made by human art is not a machine in each of its parts; for example,
far as we are concerned, and which do not have the character of a machine,
divine art and ours.
47
Even when Leibniz describes the structure of an organism in terms of a
mechanism, as he asserts in his New Essays about the bodies of plants and
animals,
48
49
This program can
-
50
51
number of organs or machines but rather the very structure of a natural ma-
ad innitum
52
something that helps us to understand in which sense Leibniz
53
and, on the
itself indestructible but also the animal itself, although its machine may often
54
In this
way, as he states in his correspondence with De Volder,
-
chines, I think it must be added at the same time that it forms one machine
46
Leibniz a Foucher, GP I, 391.
47
Loemker, 649; GP VI, 618.
48
AA VI, 6, 139.
49
, J.E. & Machines of
Nature and Corporeal Substances in Leibniz, Dordrecht-Heidelberg-London-New York: Spring-
er, 2011, p. 2.
50
Nullum quidem librum contra philosohpian Cartesianam, GP IV, 396.
51
New System, Woolhouse, 16; GP IV, 482.
52
53
Monadology, Loemker, 650; GP VI, 619.
54
Monadology, Loemker, 651; GP VI, 620.
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58
composed of these machines and that it is actuated, besides, by one entele-
chy, without which it would contain no principle of true unity.
55
-
of things that are not always artifacts at the same time, smaller machines or
-
-
56
Each part of a living being, in this
sense, is a smaller living being that is also composed of other even smaller
living beings, conforming an aggregate of machines of nature that are inte-
grated by virtue of an intrinsic teleological organization.
57
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Some remarks about Leibniz’s critics to mechanics
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