1 Introduction

Recent studies on the phenomenon of symbiosis have shown that animals are composed of many living species that develop and evolve together. These discoveries transform the classic conception of biological individuality as an autonomous organism, and have led to alternative theories such as the holobiont theory (Gilbert and Tauber 2016). These studies have not only highlighted the great complexity of the microbial world, but more fundamentally, they reveal the complex and intermixed relationships that exist between macroscopic and microscopic life (Gilbert et al. 2012). As Huneman claims, ‘any account of biological individuals has to make sense of the possibility of nestedness, i.e., of making up individuals on the basis of other individuals’ (Huneman 2014a). Researches in the fields of ecology and immunilogy have come to similar conclusions in regards to the problem of biological individuality (e.g. Gilbert et al. 2012; Pradeu 2010, 2016).

The view of nature as a game of microcosm/macrocosm relationship is an idea as old as philosophy itself. This view was very widespread in the Renaissance. The German philosopher G. W. Leibniz (1646–1716) develops this idea under the influence of the emerging life sciences and the work of the microscopists and naturalists of his time. Understanding the strongly biological character of Leibniz’s Monadology remains a challenge for interpreters.Footnote 1 One of his most original ideas is his conception of the living individual (i.e. the corporeal substance) as a network of living beings who have relationships of dependence and harmony among themselves and who share the same environment (the organic body of that higher living being).Footnote 2 In light of the recent studies mentioned at the beginning, the Leibnizian conception of biological individuality and complexity is very current. As I will show in this paper, this conception of the living being and nature has a strong ecological character.

In the following, my objective will be to analyze the textual bases that justify an ecological reading of the Leibnizian conception of biological complexity and individuality.Footnote 3 I will comment on the paragraphs of the Monadology where Leibniz presents his conception of the natural world by illustrating the idea of biological infinitism (§§ 63–70). In the second section I will present the different versions where Leibniz exposes this idea starting with his youth until his last years of life. I will summarize the main characteristics of Leibniz’s conception of the biological world and its infinite levels of complexity and individuality. The third section focuses on explaining the three characters from which Leibniz defines the organic body of living beings: the ideas of living mirror, divine machine and natural automaton. In the fourth section we will see how Leibniz explains the differentiation and individuation of organic bodies in relation to the environment they inhabit. This is where the ecological sense of the idea of biological infinitism appears since, as we will see, the relations between living individuals that constitute the natural order (both inside and outside the organic bodies) are defined from the calculation of means and ends that these individuals make in order to fulfill their biological functions. In this sense, the natural order expresses the harmony and dependence that links the infinite levels of individuality that articulate the infinite present (but also past and future) theaters where life is staged. The Leibnizian ideas of harmony, coordination or order between living individuals can therefore be interpreted from an ecological perspective. The fifth and final section will be devoted to the conclusions. In this section I will deal with the question whether in the context of Leibnizian thought an ecosystem or a community of living beings could acquire certain individuality as claimed by recent studies in the philosophy of biology.

2 Variations of the idea of biological infinitism

In the paragraphs that I will comment next, Leibniz introduces and develops his biological-philosophical thought in the context of his Monadology. Leibniz conceives the monad (i.e. the substance) as a living individual.

63. The body belonging to a Monad (which is its entelechy or its soul) constitutes along with the entelechy what may be called a living being, and along with the soul what is called an animal. Now this body of living being or of an animal is always organic […] (Monadology, 1714: GP VI, p. 618; trans. Latta 1898, p. 253).Footnote 4

It is true that in my opinion all that can truly be called a substance is a living being (Je Vous suis obligé, 1716: GP VI, p. 624; my own translation).

Leibniz’s interest in the investigations of physicians, physiologists, anatomists and microscopists of the time did not stop growing throughout his life, gradually penetrating his thinking to become a key piece in the theoretical gear of his metaphysics (see: Becchi 2017; Smith 2011, pp. 142–153; Wilson 1995). What I would first like to call attention to is the well-known and recurring speculative motif through which Leibniz is exposing his idea about the biological complexity of nature. In the Monadology we find it in paragraphs 66 and 67:

66. Whence it appears that in the smallest particle of matter there is a world of creatures, living beings, animals, entelechies, souls.

67. Each portion of matter may be conceived as like a garden full of plants and like a pond full of fishes. But each branch of every plant, each member of every animal, each drop of its liquid parts is also some such garden or pond (Monadology, 1714: GP VI, p. 618; trans. Latta 1898, p. 256).

Similar formulations can be found both in his earlier as well as older texts, for example:

Because it has to be known that, as the famous microphages Kircher and Hooke observed, a very sharp-eyed person should observe most of the things we perceive in the larger things with proportion in the minor things; if these continue to infinity - which is certainly possible, since the continuum is divisible to infinity - any atom would be like a world of infinite species and there would be worlds in other worlds at infinity (Hypothesis Physica Nova, 1671: A VI, 2, pp. 241–242; my own translation).

[…] in a fish pond there are many fishes and the liquid in each fish is, in turn, a certain kind of fish pond which contains, as it were [velut], other fishes or animals of their own kinds; and so on to infinity (Notes on Some Comments by Michel Angelo Fardella, 1690: A VI, 4, p. 1671; trans. Ariew and Garber 1989, p. 105).

Indeed I believe that in rubbish itself there are machines of nature concealed everywhere, since nothing disordered can originate from wisest Author, and that the interior parts of masses of rubbish are not any more confused than those of a pond, even if the mass of the water appears only unformed and confused in the eyes of the person who, observing from a distance, is unaware of the multitude of fish swimming in the water (Leibniz-Stahl Controversy, 1709–1711: Dutens II, 2, p. 133; trans. Duchesneau and Smith 2016, p. 21).

Another way for Leibniz to exhibit this idea is through the well-known metaphor of the theater (see Becchi 2016):

143. The theater of the corporeal world shows us more and more in this life its elegance thanks to the very light of nature, in the time in which the macrocosm and microcosm systems have begun to be exposed through the most recent inventions (Causa Dei … 1710: GP VI, p. 460; my own translation).

Through this kaleidoscopic view of the world of gardens and fishponds Leibniz develops three characteristics of the natural world and its infinite levels of complexity and individuality: (1) there is no disorder in nature except apparently; (2) the order and activity in nature derives from the living individuals that inhabit it; (3) nature has infinite levels of biological complexity and individuality. On the other hand, this idea of biological infinitism is linked to three central problems related to Leibniz’s understanding of natural world: (1) the problem of the genesis of living beings; (2) the problem of the distinction between living bodies, non-living bodies and artefacts; and (3) the problem of the composition of the continuum.Footnote 5

3 Organic bodies and worlds of creatures

In paragraphs 63 and 64 of his Monadology, Leibniz defines three characters from which he understands the organic body of living beings: the ideas of living mirror, divine machine and natural automaton.

When Leibniz states that the monad is a living mirror (or a mirror of the universe), he means that the monad contains, expresses or perceives the whole universe. However, the monad does not perceive or express all things with the same clarity; this limitation defines its particular point of view. From paragraph 56–63 Leibniz develops this idea of the living mirror from three different but complementary perspectives:

  1. (a)

    theological perspective (§ 56), based on his theory of pre-established harmony;

56. Now this connexion or adaptation of all created things to each and of each to all, means that each simple substance has relations which express all the others, and, consequently, that it is a perpetual living mirror of the universe (Théod. 130, 360.).

57. And as the same town, looked at from various sides, appears quite different and becomes as it were numerous in aspects [perspectivement]; even so, as a result of the infinite number of simple substances, it is as if there were so many different universes, which, nevertheless are nothing but aspects [perspectives] of a single universe, according to the special point of view of each Monad (Théod. 147.) (Monadology, 1714: GP VI, p. 616; trans. Latta 1898, p. 248).

  1. (b)

    mechanical perspective (§ 61), based on his conception of space as a plenum (there is no vacuum) and on his idea of actual division of matter to infinity;

61. And compounds {i.e. aggregatum of monads, i.e. bodies} are in this respect analogous with [symbolisent avec] simple substances {i.e. monads}. For all is a plenum (and thus all matter is connected together) and in the plenum every motion has an effect upon distant bodies in proportion to their distance, so that each body not only is affected by those which are in contact with it and in some way feels the effect of everything that happens to them, but also is mediately affected by bodies adjoining those with which it itself is in immediate contact. Wherefore it follows that this inter-communication of things extends to any distance, however great. And consequently every body feels the effect of all that takes place in the universe, so that he who sees all might read in each what is happening everywhere, and even what has happened or shall happen, observing in the present that which is far off as well in time as in place: σὐμπνοια πἀντα, as Hippocrates said. But a soul can read in itself only that which is there represented distinctly; it cannot all at once unroll everything that is enfolded in it, for its complexity is infinite (Monadology, 1714: GP VI, p. 617; trans. Latta 1898, p. 251–252).

  1. (c)

    and finally, physiological perspective (§ 63), based on his definition of the organic body.

62. Thus, although each created Monad represents the whole universe, it represents more distinctly the body which specially pertains to it, and of which it is the entelechy; and as this body expresses the whole universe through the connexion of all matter in the plenum, the soul also represents the whole universe in representing this body, which belongs to it in a special way (Théod. 400.).

63. The body belonging to a Monad (which is its entelechy or its soul) constitutes along with the entelechy what may be called a living being, and along with the soul what is called an animal. Now this body of living being or of an animal is always organic; for, as every Monad is, in its own way, a mirror of the universe, and as the universe is ruled according to a perfect order, there must also be order in that which represents it, i.e. in the perceptions of the soul, and consequently there must be order in the body, through which the universe is represented in the soul (Monadology, 1714: GP VI, p. 618; trans. Latta 1898, p. 253).

This last definition of the idea of the living mirror is the one that interests us most. This idea of the ‘living mirror’, actually a quality of the monad, refers to the existence of an order in the body of the living being according to which the universe is represented in (or expressed by) the soul. Leibniz calls this order of the living body ‘organic’. For Leibniz the monads are not in space, nor do they flutter senselessly in the world, but rather acquire a position in the universe thanks to the body that belongs to them (GP II, pp. 250–253). The body is the anchor of the monad in the world that determines its place, or its point of view. Moreover, if the monad had no organic body, it would lack activity (perception and appetite), or, in other words, every monad is, in a sense, incorporated.

Leibniz highlights here the characteristic dynamics of a living body, which is its perceptive capacity. There is a correspondence or harmony between the organic complexity of the living body (its organism) and the order of its surrounding world (the environment). This is for Leibniz the basis of the animal’s sensitivity. What the soul perceives is precisely this correspondence. The correspondence or harmony between the organism and its environment is in turn expressed as correspondence or harmony between the states of the body and the states of the soul.Footnote 6

25. We see also that nature has given heightened perceptions to animals, from the care she has taken to provide them with organs, which collect numerous rays of light, or numerous undulations of the air, in order, by uniting them, to make them have greater effect. Something similar to this takes place in smell, in taste and in touch, and perhaps in a number of other senses, which are unknown to us. And I will explain presently how that which takes place in the soul represents what happens in the bodily organs (Monadology, 1714: GP VI, p. 611; trans. Latta 1898, p. 231–232).

[…] and yet it remains true that, when the organ and the medium are constituted as they should be, the internal motions and the ideas which represent them to the soul resemble the motions of the object which cause color, heat, pain, etc., or, what is here the same thing, express it by means of a relation sufficiently exact, although this relation does not distinctly appear to us, because we cannot disentangle this multitude of small impressions either in our soul or our body or in what is without (New Essays, 1704, book II, VIII-21; trans. Langley 1896, p. 134).

In the following paragraphs of the Monadology, Leibniz continues with the definition of the organic body as a ‘divine machine’ and a ‘natural automaton’. This definition emphasizes the difference with artificial machines. As illustrated in the paragraph below, the first notion (the divine machine) refers to the complexity of the body by picking up the idea that ‘living bodies are machines in their minimum parts to infinity’.

64. Thus the organic body of each living being is a kind of divine machine or natural automaton, which infinitely surpasses all artificial automata. For a machine made by the skill of man is not a machine in each of its parts. For instance, the tooth of a brass wheel has parts or fragments which for us are not artificial products, and which do not have the special characteristics of the machine, for they give no indication of the use for which the wheel was intended. But the machines of nature, namely, living bodies, are still machines in their smallest parts ad infinitum. It is this that constitutes the difference between nature and art, that is to say, between the divine art and ours.

65. And the Author of nature has been able to employ this divine and infinitely wonderful power of art, because each portion of matter is not only infinitely divisible, as the ancients observed, but is also actually subdivided without end, each part into further parts, of which each has some motion of its own; otherwise it would be impossible for each portion of matter to express the whole universe (Monadology, 1714: GP VI, p. 618; trans. Latta 1898, pp. 254–255).

Unlike artificial machines, natural or divine machines ‘are still machines in their smallest parts ad infinitum’. Is this the only difference between them? What kind of machine does Leibniz have in mind when he talks about divine machines? The answer can be found in the following two paragraphs (66 and 67, cited above), in which Leibniz exposes his idea of biological infinitism. The complexity of the natural machine has to be understood then from the idea of the worlds of creatures and not by analogy with the artificial machines.Footnote 7

The third notion with which Leibniz characterizes the organic body is the ‘natural automaton’. The word ‘automaton’ is mentioned elsewhere in the Monadology in reference to the monad or simple substance, which Leibniz defines as ‘incorporeal automaton’. Leibniz makes use of both ideas of automaton (natural and incorporeal) to separate himself from N. Malebranche’s theory of occasionalism. Contrary to Malebranche’s opinion, Leibniz affirms that God has introduced a force into the corporeal substances that makes them capable of acting by themselves, and that there is no need for God to be continuously interacting with his creatures as if they were puppets.

11. It follows from what has just been said, that the natural changes of the Monads come from an internal principle, since an external cause can have no influence upon their inner being (Théod. 396, 400) […].

18. All simple substances or created Monads might be called Entelechies, for they have in them a certain perfection (ἔχονσι τό ἐντελεϛ); they have a certain self-sufficiency (αὐτάρκεια) which makes them the sources of their internal activities and, so to speak, incorporeal automata (Théod. 87.) (Monadology, 1714: GP VI, pp. 608–610; trans. Latta 1898, pp. 223–229).

But this same idea also applies to bodies (e.g. GP IV, p. 397), including organic bodies. In the case of organic bodies, as Leibniz says to G. E. Stahl, this internal principle is the organism itself, which by the same ‘force of its structure’ is capable of fulfilling by itself (without intervention of the soul or God) the essential biological functions for its conservation: vegetation, nutrition and reproduction.

The celebrated author {Stahl} instead places it {life} in that very ability of guarding one’s own body against the propensity for destruction […] I have referred this back to the force of vegetating, by which the living body perfects, nourishes, repairs, and propagates itself, and this, I maintain, follows from the very structure of the machine {i.e. the organism}, even if everywhere the soul is conspiring (Leibniz-Stahl Controversy, 1709–1711: Dutens II, 2, pp. 137–138; trans. Duchesneau and Smith 2016, p. 35).

This self-sufficiency of natural machines, which makes them capable of keeping themselves alive and creating a copy of themselves, differentiates them from artificial machines. Such capacity does not derive from the fact that natural machines are more complex artefacts, even infinitely complex. As we have seen in paragraphs 66 and 67 of the Monadology, Leibniz understands the organic complexity of the living being from the idea of the worlds of creatures which imply a conception of order that extends between, or depends on, a set of living beings that is not reducible to mechanical explanations. The force of the organism to preserve itself in existence as well as reproduce itself has its origin in the hierarchical set of living beings (i.e. corporeal substances) that are linked to the same organic body. As we shall see, the logic underlying the relationship between living beings always passes through the organism-environment correspondence or harmony, which is different from the logic that links the mechanical parts in a human artefact.Footnote 8 I develop this subject in the next section when I speak of the idea of subordinate and dominant monads.

Leibniz tells us in various fragments that bodies are resolved into, or composed of, corporeal substances (e.g. Couturat, p. 14, A VI, 4, p. 1671 or GP III, p. 260). Should we interpret this idea as if the corporeal substances were parts of the organism where they live?

For Leibniz the monads or substances contained in the organic body of a higher organism are not parts of it, but requisites.

A body is not a substance but an aggregate of substances, since it is always further divisible, and any given part always has another part, to infinity. […] Hence, unless there are certain indivisible substance, bodies would not be real, but would only be appearances or phenomena (like the rainbow), having eliminated every basis from which they can be composed. However, from this, one must not infer that the indivisible substances enters into the composition of body as a part, but rather as an essential, internal requisite, just as one grants that a point is not a part that makes up a line, but rather something of a different sort which is, nevertheless, necessarily required for the line to be, ant to be understood (Notes on Some Comments by Michel Angelo Fardella, 1690: A VI, 4, pp. 1668–1669) trans. Ariew & Garber 1989, p. 103).

Leibniz defines this idea of a requisite by analogy with the relationship between the point and the line. According to Leibniz, points are not parts of a line but requisites of it. Every part we take from a line (as every extensive body) will be divisible. In contrast, points are by definition indivisible (and inextensive, as a substance is). The point is by definition the principle of composition of a line, without which the line would not be intelligible. These ideas connect us to the problem of the composition of the continuum, which I will return to later.

Although monads are not parts of the higher organism they inhabit, their organic bodies could be functional parts (i.e. organs) of that higher organism. Leibniz himself warns us that this reading is not possible.

It is true that in a heart and in any part of an animated body, indeed in any given mass, complete organic bodies {organic bodies with souls, i.e. living beings} are inherent, even if most of the time they cannot be sensed, and that these bodies are animated or actuated by themselves. And unless this were the case, matter could not be actuated anywhere, nor could mechanism itself occur. (18) But it is not the case that any given part of an organic body is an {complete} organic body: thus, although a heart retains its motion for a certain amount of time after it has been torn out of the body, it is not proved from this that the heart is an animated body, for a mere mechanism suffices for some continuation of this motion, even if perception and appetite are wanting (Leibniz-Stahl Controversy, 1709–1711: Dutens II, 2, p. 157; trans. Duchesneau and Smith 2016, p. 331).

The advantage of an ecological reading of the idea of the divine machine on the basis of the image of worlds of creatures is that it prevents us from reducing the complexity of the natural machine to the complexity of human artefacts, which is what happens when we identify the small living beings or their organic bodies as parts of higher organisms, and which would make living organisms only infinitely complex artefacts.Footnote 9 If we cannot understand as parts neither the living beings contained in a natural machine, nor their organic bodies, then the relationship of these living beings to each other and to the higher organism they inhabit cannot be understood in a mereological way. In the next section we will see how Leibniz understands these relationships and why we can interpret them ecologically.

There is also another problem that Leibniz himself emphasizes in the above quotation: ‘Hence, unless there are certain indivisible substances, bodies would not be real’. If we ignore that the organic complexity (and activity) of the bodies is based on the coordination between a set of living beings, which is what gives the organic body its reality, then we could think, following some idealistic interpretations of the Monadology, that these organic bodies that share that multiplicity of living beings is no more than an epiphenomenon derived from the representative activity of their souls. Non-animate organic bodies are something real and not just a mere phenomenon. The fact that there are non-living organic bodies does not mean that they do not contain living beings within them, but that they themselves are not a living being. This difference is also pointed out by Leibniz: everything in nature is full of ‘animated organic bodies’ or living beings, but not ‘every piece of matter is animated’, that is, it is linked to a soul and is therefore a living being, and he continues, ‘as we do not say that a fishpond full of fish is an animated body, although the fish is’ (GP VI, pp. 539–540).

The idea of biological infinitism allows Leibniz to definitively get out of the problem of the continuum. As Leibniz says in the previous quotation ‘a body […] is always further divisible, and any given part always has another part, to infinity’. This is the problem of the composition of the continuum or the labyrinth of the continuum. According to Leibniz, in order to get out of this problem and find that principle which gives reality to bodies, we cannot resort to any material principle. Because of the current division of the continuum to infinity, the extension, the figure or the movement are not ‘exact properties’ or ‘properties fixed in the bodies’. It is therefore ‘not possible to determine to which body these properties belong’. For Leibniz these are properties that are not real, but ‘involve something of the imagination’ (A II, 2, p. 187). That is why Leibniz often states that the foundations of mechanism cannot be mechanical in turn. The principles underlying the origin and foundation of the order and activity that we observe in natural bodies have to be true indivisible units (not aggregates of parts), permanent (not successive) and absolute (not relative). Leibniz calls these principles monads or substances. But if matter needs substances to be something real, we must not forget that substances which are simple and inextensive can only be expressed in their corresponding organic bodies which are composed and extensive and without which substances would not be intelligible and not even possible. That is why ‘nature is full of living organic bodies’ (GP VI, p. 550).

Monads, and more specifically the relations between them (defined as harmony, correspondence, domination), are the principles of composition of the continuum. The questions to be answered next are: what kind of relationship is this that takes place between monads or substances, what is its nature and how does it take place, can it be interpreted in an ecological way?

4 Order and harmony among living beings. Teleology and domination

In the following paragraphs 68 and 69 of the Monadology Leibniz introduces some of the ideas we have just seen in relation to the difference between animate (or complete) and non-animate organic bodies.

68. And though the earth and the air which are between the plants of the garden, or the water which is between the fish of the pond, be neither plant nor fish; yet they also contain plants and fishes, but mostly so minute as to be imperceptible to us.

69. Thus there is nothing fallow, nothing sterile, nothing dead in the universe, no chaos, no confusion save in appearance, somewhat as it might appear to be in a pond at a distance, in which one would see a confused movement and, as it were, a swarming of fish in the pond, without separately distinguishing the fish themselves. (Monadology, 1714: GP VI, pp. 618–619; trans. Latta 1898, pp. 256–257. See also GP VI, pp. 539–540).

Regardless of the degree of clarity with which we manage to observe the existing order in every organic body, Leibniz tells us that in truth there is no portion of organic matter where there is no order nor life on which that order depends. Every piece of organic matter is full of life, of animated creatures, whose activity is responsible for the order we observe. Following Leibniz, each environment shared by a group of living beings is something real and not something merely imaginary.

As claimed at the beginning of the Monadology, the living beings, the monads, do not have windows, that is, there is no direct communication from substance to substance. The relations between them are mediated, firstly, by the organic body that corresponds to each of those living beings and, secondly, by the environment they share. Here again emerges the question raised earlier about the kind of relationship that Leibniz is referring to in the case of living beings who share the same organic body.

Perhaps the most representative quotation of Leibniz’s notion of harmony and order that reigns in these ‘worlds of creatures’ is found in the controversy with the physician G.E. Stahl. In opposition to the animistic theses of Stahl, Leibniz makes an effort to explain the nature of the machine that is the organism of every living being without involving the soul. Leibniz states that the organic body of every living being is a machine ready to perform by itself certain operations: vegetation, nutrition and reproduction. Through these functions the organic bodies of living beings can ‘preserve themselves and produce a copy of themselves’ (Dutens II, 2, p. 132). According to Leibniz, this is the ‘particular end’ for which the organisms of living beings are designed. Moreover, for these ends to be fulfilled and for the living being to be able to carry out its functions, a series of external things must concur that the soul represents as means (through the organs of its body). That is, in the fulfillment of such particular end the living being is adapted to, in relation to or in harmony with, a particular environment. Leibniz says that ‘in any body the state of the surrounding things concurs with its own state’ (Dutens II, 2, p. 132).

Indeed, just as the Response {of Stahl}, by resorting to rigorous explanations, denies that a flame preserves, nourishes, propagates, and maintains itself and requires an influx of air, in the same way it can be denied that an animal accomplishes the same by itself, since without the perpetual influx of ambient elements, and without their intimate permeating of the body, not only would respiration not take place, but indeed the heat and the fluidity of the humors would cease, as is evident from the experience of intense cold. Not to mention, besides, the elastic force and tonic motion (which, I believe, is nothing other than the action of the elastic force), which, it is also evident, arise from the motion of particles permeating the body. We also know from the experiment with the pneumatic pump that by the pressure of ambient air, the blood and other liquids are generally maintained in their appropriate consistency, and that when the pressure is taken away, they become foamy and the vessels burst, nor, which is equivalent, does the blood circulate any longer. Perpetual transpiration can be added, and many other indications show that the bodies of animals not only require nourishment obtained at intervals, but also are in continual flux like a river. (Leibniz-Stahl Controversy, 1709–1711: Dutens II, 2, pp. 146–147; trans. Duchesneau and Smith 2016, pp. 279–281).

This concurrence of the surrounding things is not only necessary for the feeding, but it is a requirement for the fulfillment of the other biological functions. Among these ‘surrounding things’, Leibniz includes other living beings. This idea is taken up by Leibniz when he says that the particular ends of each of the living beings are linked to a general end that links all things as a ‘precious chain’ (Dutens II, 2, pp. 132–133). This relationship of conformity or harmony works through a calculation of means for the purposes of preservation and reproduction. Below I quote the fragment of the controversy with Stahl where Leibniz expresses this idea of harmony among the living beings:

[…] machines have {particular} ends and effects through the force of their structure {i.e., their organism}, whereas the ends and effects of aggregates {that is, a group of living beings who share in harmony the same environment} arise from a series of concurrent things and thus from the convergence of diverse machines, which, although it follows a divine design, yet implies a more or less manifest coordination; thus the silkworm’s end and initial function is the production of silk, but to generate another silkworm, it is necessary that there be congress between a male and a female, and thus that there occur the combination of one animal with some other external thing […] such as the heat of the sun, nutrition from mulberry leaves, and other things of this sort. (Leibniz-Stahl Controversy, 1709–1711: Dutens II, 2, pp. 135–136; trans. Duchesneau and Smith 2016, p. 249).

As the quotation suggests, one way to deal with the explanation of the coordination or harmony between diverse living beings could be based on biological-ecological criteria.Footnote 10 These criteria explain at the same time the order and teleology inscribed in the natural environments. Through such relationships the living beings influence one another (i.e. not directly but through the environment they share where they have to perform their biological functions). This natural influx among living beings is explained by Leibniz as changes in their degree of perfection: as they pass to greater perfection (greater distinction in their perception) then they act; otherwise, they suffer (Monadology, § 49). This graduation in perfection that binds the living beings in their mutual influence is the basis of the domination that, Leibniz claims to take place among them: ‘Thus not only is there everywhere life, accompanied with members or organs, but there is also an infinity of degrees in the Monads, one dominating more or less over another’ (Principes de la nature et de la grâce fondés en raison, 1714: GP VI, p. 599; trans. Latta 1898, pp. 409–410).

Since monads or living beings do not influence each other directly, it does not seem appropriate to interpret domination as a capacity of the living individual that can be exerted over another one according to his will. The reciprocal differentiation between the organic body and its environment explains the harmony, dependence and the domination that takes place in the aggregation of living beings. Domination is a relationship not a property; it is inscribed in the environment as a result of the history of the natural world. This history of the natural world reflects at the same time the transformations that occur in living beings and in the environment they inhabit, and that may even give rise to the appearance of new species or their extinction (see New Essays: GP V, p. 296 or letter to Thomas Burnett of Kemney: Leibniz 1993, pp. 201–202). The relations of domination determine the changes in the living beings and in the environment they share. But what happens in the case of those living beings contained in the organic body of another higher living being? In these cases, there is a substance that controls (or more correctly, expresses or contains in its perfection) the relations of domination that link these living beings with a specific goal: to constitute and maintain a higher living body. Leibniz calls this substance ‘dominant monad’, which becomes the soul or substantial form of the living body.

70. Hence it appears that each living body has a dominant entelechy, which in an animal is the soul; but the members of this living body are full of other living beings, plants, animals, each of which has also its dominant entelechy or soul. (Monadology, 1714: GP VI, p. 619; trans. Latta 1898, p. 257).

Leibniz calls ‘subordinate monads’ the substances dominated or coordinated by the same dominant monad. The ideas of dominant monad and subordinate monad are the last pieces of the theoretical gear that Leibniz took to develop his conception of the hierarchical order in the ‘worlds of creatures’. It is also the basis with which he explains the various transformations that affect the organism during its life cycle. The substantial forms of the subordinate monads are defined as ‘assistant forms’. These assistant forms have the power to transform the organic body with which they are linked (something very remarkable during the birth and death of the organism). The substantial form of the dominant monad is defined as the ‘inherent or animating form’ and its power is limited to coordinating the subordinated living organisms. As we have seen, this coordination does not happen in a direct way but always through the organic body to which both the subordinate monads and the dominant monad are united (though in a different way: for the former, it is their natural environment; for the latter, the organism to which it is linked) (for all the above see GP II, p. 320).

In this Leibnizian conception of nature as infinite worlds of creatures, some within others and some unfolding from others, domination, harmony and dependence extend between living beings both horizontally, that is, between those living beings who share the same environment, as well as vertically, in connection with the subordination of a network of living beings to the same dominant monad.

It is important to emphasize that for Leibniz an organism not only needs the presence of a dominant monad whose soul is the ‘immanent form’ that makes all the inferior organisms that inhabit its body ‘behave according to the natural order’ (GP II, p. 320); at the same time it requires the presence of the ‘assisting forms’ of each one of those (infinite) inferior organisms, which have the ‘power to transform the body’ (GP II, p. 320), and, which are responsible for the genesis and maintenance of the higher organism.

[…] along with the entelechy, I don’t put anything into the monad or the complete simple substance, but the primitive passive force that is related to the whole mass of the organic body, of which the rest of the subordinate monads that are in the organs are not a part but immediate requisites for its constitution and concur with the primary monad {i.e. the dominant monad} for the formation of the organic corporeal substance, be it animal or plant. (Letter from Leibniz to De Volder, 20 June 1703: GP II, p. 252; my own translation).

In the seed of large animals there are animacules which by means of conception obtain a new outward form, which they make their own and which enables them to grow and become larger so as to pass to a greater theatre and to propagate the large animal. […] Animals change, take on and put off, parts only. In nutrition this takes place gradually and by little imperceptible [insensible] portions, but continually; and on the other hand, in conception or in death, when much is gained or lost all at once, it takes place suddenly and in a way that can be noticed [notablement], but rarely. (Principes de la nature et de la grâce fondés en raison, 1714: GP VI, pp. 601–602; trans. Latta 1898, pp. 413–414).

An ecological interpretation of the idea of biological infinitism based on texts such as the Stahl controversy cited above allows us to understand how living organisms are composed of or resolved into a hierarchical network of living beings, and how that coordination of living beings takes place so as to explain the complexity and dynamic of the living organism.

5 Conclusions

Leibniz’s growing research in life sciences of the time forced him in his last years, more or less consciously, to rethink the ideas of unity and individual. In his Monadology, Leibniz provides an understanding of biological individuality that involves infinite hierarchical levels of living individuals. This is one of the most original points in Leibniz’s metaphysics. The first interpreter to understand the originality of Leibniz’s biological conception of individuality was L. Feuerbach. In his 1837 text entitled ‘Darstellung, Entwicklung und Kritik der Leibniz’schen Philosophie’, he shows a special sensitivity when it comes to understanding the model of individuality that is behind the metaphysical project of Monadology. Feuerbach explains the individuality of the monad by analogy with the bee hive model: this conception of the individuality consists of an infinite network of living beings entering subordination-domination relationships in a particular environment. For Leibniz, as we have seen, an organism is an infinite world of creatures that plays a constitutive role in their individual and biological being. The individuality of a living organism as well as the complexity of any natural environment is explained on the basis of the network of relationships (of subordination and domination) that extends between a set of living beings. It is this network of relations that manages to understand the totality of the organic body (in an organisational but also in a genetic sense).

The ecological interpretation that I propose in regards to the idea of biological infinitism has certain advantages. It takes into consideration the centring value that the idea of biological infinitism has in the monadological metaphysics. It is more faithful to the idea that monads are not parts but requisites of the higher organism they inhabit. It does not contradict the epistemological value that Leibniz confers to the mechanistic understanding of organic bodies. And finally, it provides a simple way to explain the coordination or harmony between a set of monads or living beings that share the same environment including the ideas of dominant and subordinate monads.

In addition to the interest that Leibniz’s biological thinking may arouse among specialists, his intuitions have been and continue to be a source of inspiration for researchers. A good example of this is found in a series of recent works by Huneman (2014a, b, c) which are dedicated to the problem of biological individuality. There are more and more studies today that show the difficulty to delimit where an individual or an organism begins and where another ends in nature. I quoted some of them in the introduction of this paper. To address the problem of biological individuality, Huneman follows a strategy inspired by Leibniz, whom he quotes in his work. Even if we cannot say that an ecosystem or a community is an individual in a strong sense (that is, according to the evolutionary concept of individual), Hunemann argues that another concept of individual must exist to differentiate between communities or ecosystems and a mere random gathering of individuals or species. Given the growing experimental evidence, Huneman recognizes the need that the philosophy of biology has to confer some kind of individuality to communities and ecosystems, and which he also refers to with the term ‘nested individuals’. Huneman speaks in this line of a ‘weak individuality’. According to Huneman, this idea of weak individuality has certain advantages over other ideas such as superorganism.

Following Huneman’s reflection, we can finally consider whether Leibniz confers certain individuality to the aggregates of living beings that would make up the worlds of creatures (i.e. what we understand by ecosystems today). Like Huneman, Leibniz recognizes that an ordered community has more unity than a confused crowd, but less than an organized body (Finster, p. 265). However, Leibniz only considers the organic body endowed with a dominant monad or soul (i.e. a living being) as an individual or a true unity. Worlds of creatures and the environments they share are ‘entities or unities by aggregation’. More specifically, Leibniz refers to them as ‘substantiated beings’.Footnote 11 These substantiated beings are real and possess a certain unity according to the relationships existing in the aggregate of living beings they contain. But, according to Leibniz, they contain something of the imaginary. This is due to the fact that in the framework of the idea of biological infinitism, where matter is currently divided into infinity and the worlds of creatures fold into each other indefinitely, the limits that differentiate between some aggregates of living beings and others are partially delimited by our imagination. This does not mean that they are a phantom of the mind, but that they belong to the order of phenomena (‘well founded’, as Leibniz calls them). Following Huneman’s idea, we can apply the term ‘weak individuality’ to Leibniz’s understanding of the aggregates of living beings that share the same environment. These communities of living beings or ecosystems would represent the subject of that natural history to which Leibniz refers in some passages of his Protogaea and his New Essays—a natural history that contains the joint evolution of biological species and their environments (Dutens, II, 2, pp. 220, 229 and GP V, p. 296). We could even understand this individuality in Leibnizian terms as the set of predicates that account for the parallel evolution of a series of biological species alongside the environment they share.