1. Introduction: Leibniz and the Completion of Metaphysics
Gottfried Wilhelm, Freiherr von Leibniz (1646–1716) is one of the most extraordinary figures in the history of ideas. A true polymath, he was not only a philosopher but a physicist, historian, jurist, diplomat, inventor, and mathematician. Perhaps the most celebrated of his achievements was the discovery of the differential and integral calculus, which he discovered independently of Newton (it is common now to credit both for the achievement, though at one time this was controversial).
However, it is to Leibniz’s achievements as a philosopher that we must confine ourselves, and here we can only scratch the surface. Leibniz’s philosophy is one of the most bizarre creations in intellectual history. To some it might seem like a reductio ad absurdum of the “rationalist” approach inaugurated in philosophy by Descartes. In his extremely useful essay “Leibniz: An Introduction,” Jacob Klein (a student of Heidegger) characterizes Leibniz’s philosophy as a “phantasmagoric spectacle” and as a “systematic monstrosity.”   This is all true, yet it is a fascinating monstrosity, chiefly for two reasons.
First, Leibniz’s philosophy demonstrates the consequences of the representationalist  approach, carried to its ultimate extreme. In doing so, it advances the modern inflection of what we have characterized in previous essays as Heidegger’s theory of the “metaphysics of presence .” Indeed, Heidegger regarded Leibniz as a figure of extraordinary importance, devoting a number of seminars and essays to him. Second, Leibniz is fascinating for how much he anticipates — or, perhaps we should say, makes possible — in later philosophy. Heidegger writes,
The full beginning of the history of Being in the form of modern metaphysics occurs where the essential completion of Being determined as reality is not yet accomplished as such, but where the possibility of the decisiveness of this completion is totally prepared for, and the ground of the history of completion thus laid. To take upon himself this preparation of the completion of modern metaphysics, and thus everywhere to rule this history of completion, is the determination of the history of Being of that thinking accomplished by Leibniz.  
This is a particularly turgid and difficult statement, but what it essentially means is that Leibniz prepares the completion of modern metaphysics but does not actually bring it about (for Heidegger, the actual completion is accomplished by Nietzsche). In what way does Leibniz prepare the way? Basically, by establishing certain patterns of thought, the implications of which will be spelled out or developed by later philosophers. This is particularly the case with German philosophy.
It is with Leibniz, not with Kant, that the tradition of “German idealism” truly begins. And we may make a stronger point: with Leibniz, the history of metaphysics becomes essentially the history of German philosophy. Thus, to say that Leibniz plants the seeds of later developments in German thought is saying something more than that he influenced just one particular branch of philosophy, or one nation’s philosophy. In that sense, Leibniz “rules” over the history of the completion of metaphysics. After Leibniz, all the most profound and important work in metaphysics is carried out by Germans. This is also arguably true for philosophy as a whole.
To be sure, there are non-German philosophers of note in the history of modern philosophy. But, for the most part, they are significant merely because they influenced others, or posed problems that were taken up by other, more profound (and more German) philosophers. An excellent example of this is British empiricism — a thoroughly wrongheaded approach to philosophy, the most significant result of which is that some of the problems it posed awakened Kant from his “dogmatic slumber.” The importance of British empiricism consists in this, and in how the ideas of these philosophers (chiefly Locke, Berkeley, and Hume), which were highly influential in multiple disciplines, reflect problematic and quintessentially modern assumptions. Because the empiricists have nothing profound or interesting to say about Being, they merit almost no attention from Heidegger at all. (Hegel and the other great German philosophers also mostly ignore them; Kant is the exception.) Nevertheless, I may have something to say about the empiricists in a later installment.
Turning now to Leibniz’s ideas, we are faced with the problem of where to begin. Leibniz left behind no complete and detailed statement of his philosophy. He produced mostly short, cryptic works which presented his ideas in summary fashion, such as The Discourse on Metaphysics (1686) and Monadology (1714), the chief texts I will draw upon in the discussion that follows. Presenting an account of Leibniz’s philosophy involves piecing together the ideas in these texts, and in Leibniz’s correspondence, and trying to reconcile them, since they present many apparent inconsistencies. Still, for our purposes there is an obvious starting point. Since this series is an account of the “history of metaphysics” or, alternatively, the “history of Being,” we should begin with how Leibniz understands Being.
By the time Leibniz set down his ideas, Being had come to be referred to by philosophers as “substance.” During the Middle Ages, the Greek word for Being, ousia, came to be Latinized as substantia. This term is derived from the present active participle of substō, which literally means “to stand under.” Substance is thus what stands or abides beneath. Beneath what? The answer to this question is crucial. Beneath the appearances? Beneath a thing’s “accidental” (as opposed to essential) properties? “Beneath,” or throughout, change? Here modern philosophers differ. But, setting specific theories aside, we may simply say that substance means what is, or what truly is.
The introduction of the term “substance” was unfortunate, for a variety of reasons. Not least of these is that undergraduate students of philosophy invariably misunderstand it as referring to some kind of plastic “stuff” (as in, “What substance is this made out of?”). It does not mean this, however. Again, it simply means “what is.” The term is used by Descartes when he distinguishes two types of beings: extended substance (i.e., bodies; “extended” in the sense of occupying space, being three-dimensional), and unextended substance (mind, which Descartes held did not occupy space). The term is famously taken up by Spinoza, who argued that there is only one substance, one being, God, whose chief attributes correspond to Descartes’s substances: “thought” and “extension.” The term is also present in Locke, Berkeley, and Hume, who understand substance as the “substratum” of a thing underlying its perceptible qualities (though Berkeley and Hume reject the idea of substance as unintelligible or unverifiable). We even find the term in Hegel.
Leibniz’s definition of substance builds upon the entire Western philosophical understanding of Being from Parmenides until his own time. This tradition holds that Being is “convertible” with the good, the true, and the one, i.e., all these ideas are equivalent to one another. Thus, whatever “is” (or truly is) may also be said to be good, true, and one. In defining substance, Leibniz focusses upon the characteristic of unity, or being a one. Whatever can be said to be truly one is a true substance or being. But how can we discover what that is?
2. Being as Mind
Leibniz begins with the simple observation that everything we are aware of is a composite. In other words, it is made of parts. For example, there is a wooden box on my desk. It is composed of four primary pieces: a bottom, a lid, and four sides. I could, if I wished, break the box down into these parts. And I could keep breaking those parts down as well. If I had fine enough tools and quite a lot of time, I could keep decomposing the parts of the box into still smaller parts. But could this process continue infinitely? Leibniz argues that it is nonsensical to think that it could: there must be some ultimate constituent all these parts are composed out of. This ultimate constituent, to be ultimate, would have to be simple rather than composite. In other words, it could not be broken down into further, smaller parts.
So far this sounds like an argument in favor of atomism, which is an ancient theory: all things are composed, ultimately, out of tiny, indivisible atoms (which literally means, in the original Greek, “uncuttables”). But Leibniz then surprises us with an obvious point. Anything that is simple or incomposite would not actually occupy space. Things take up space (they occupy three dimensions) in virtue of being “extended”; i.e., in virtue of having parts. Anything that was truly simple would therefore have no dimensions at all. But this means that the “ultimate constituents” of which composites are “made” would have to be nonmaterial. Leibniz’s argument seems logical, but it leads to a major problem: how can material things be composed of non-material objects? We could “put together” (whatever that might involve) as many simple substances as we like, but if none of them occupies space we cannot derive from them a composite that does occupy space. It would be like adding up strings of zeros thinking that eventually we will arrive at a value greater than zero.
At this point, we have to either reject Leibniz’s argument that the ultimate substances are dimensionless, or we have to reject the belief in material composites. Since Leibniz believes his argument to be sound, he rejects the existence of material bodies existing independently of the mind.
Substances, for Leibniz, are not unlike geometrical points, defined by Euclid as “that which has no parts.” However, what we are dealing with is, in fact, “metaphysical points” (as both Klein and Frederick Copleston describe the Leibnizian substances  ). Unlike geometrical points, Leibniz insists that his substances must also be unique. This follows from his principle of the “identity of indiscernibles”: if any two beings were exactly alike then they would not be two beings but one. Therefore, each substance must be different, at least in some ways, from every other.  
Leibniz says, along with all the metaphysicians that preceded him, “Being is one.” But this does not mean that there is only one being; rather, for Leibniz, there are infinitely many ones, each different from all the others.   So, summing up, substance/being, for Leibniz, is one, simple, unique, and infinitely many. Let us also not forget that the characteristic of being simple entails that substances are incorporeal (i.e., immaterial). So far so good, but what exactly answers to this description? What are these substances? And how exactly are they differentiated from each other?
Well, the characteristics that make each substance different from all the others obviously cannot be physical properties such as color, shape, size, weight, or location. So, by process of elimination, what differentiates substances from each other must have something to do with their acts. Indeed, Leibniz says that they must be in act. And to refer to this state, he borrows the term entelecheia from Aristotle, which is loosely translated as “actuality.” Aristotle had reasoned that a being, to be a true being, must not be potentially something or other but must have achieved actuality. To potentially be x is to not yet be x; to actually be x means to have achieved xness, or be in the act of being x. Thus, Leibniz reasons that his substances must be doing something, something that makes them what they are. Since this can’t be a physical doing, it must, again by process of elimination, be a mental doing. Substances must be minds.
These minds do what minds do: they perceive, they are aware. Leibniz uses the term monad to describe his substances, which comes from the Greek monas meaning “unit.” Though all of Leibniz’s monads may be understood as minds, not all are “human souls.” Only those minds that are capable of self-awareness, of knowing that they know, are human minds. Leibniz uses the term apperception to refer to this power of knowing that we know.   The term is more famously associated with Kant, who borrows it (and much else) from Leibniz.
But what is the nature of the monads’ perception? Since Leibniz has ruled out the existence of a material world, just what do the monads perceive? Leibniz accepts from Cartesian representationalism the idea that the object is literally what is “thrown against” us (see part four  of this series). However, as Klein astutely observes, “In Leibniz’s way of speaking . . . what is perceived by us is what we ourselves throw out of us and put before us — not an ob-jectum but a pro-jectum, as it were. Now, this act of pro-jecting is, according to Leibniz, the very activity of Being as such, of substance. And it is this activity that Leibniz means when he speaks of ‘perceiving’ or of ‘perception.’”  
So, the action or doing of the monads is perceiving. But what Klein has said seems to imply that the monads create their own perceptions. Thus, Leibniz seems to be some kind of strange subjectivist who does not belong to the representationalist tradition at all, since he does not think perceptions represent anything external to the mind. This first impression is quite wrong, however. For Leibniz my perceptions do, in some sense, have an object, but that object is not a “physical world.” Instead, it is the other monads or minds — or, at least, their perceptions. For Leibniz, the only world “external” to my monad is the metaphysical world in which other monads exist independently of me. My perceptions re-present the perceptions of all the other monads, but from a unique point of view. Each being is in act: it perceives. Each perceives the perceptions of all the other monads, but from a unique and unrepeatable perspective. This is how each monad is differentiated from every other.
Leibniz expresses this bizarre idea in a number of striking formulations. In the Discourse on Metaphysics, he writes that
[Every] substance is like a complete world and like a mirror of God or of the whole universe, which each one expresses in its own way, somewhat as the same city is variously represented depending upon the different positions from which it is viewed. Thus the universe is in some way multiplied as many times as there are substances, and the glory of God is likewise multiplied by as many entirely different representations of his work.  
(We will shortly see how God fits into Leibniz’s metaphysics.) Elsewhere in the same text, he writes that “every person or substance is like a small world expressing the large world” (in other words, we have here the perennial identification of the microcosm and the macrocosm).   In the Monadology, Leibniz expresses himself similarly, saying that
each simple substance has relations that express all the others, and consequently, [each] simple substance is a perpetual, living mirror of the universe. Just as the same city viewed from different directions appears entirely different and, as it were, multiplied perspectivally, in just the same way it happens that, because of the infinite multitude of simple substances, there are, as it were, just as many different universes, which are, nevertheless, only perspectives on a single one, corresponding to the different points of view of each monad.  
Thus, each monad contains within itself an entire universe — the entire universe. Yet there is no universe independent of the monads’ perceptions of it. This does not mean that Leibniz held that the world is an “illusion.” Rather (somewhat like Berkeley, in fact) he held that these perceptions are the universe. His position is the exact reverse of Aristotle’s, whom I discussed in part one  of this series. Aristotle held that the mind (or intellect, nous) is potentially all things; mind is nothing in itself, but is rather a kind of container that has the potential to receive the intelligible forms of all that exists. For Leibniz, on the other hand, mind is actually all things, for all that exists is contained within it.
However, there is still potentiality within our minds, Leibniz makes clear. Though your monad contains the entire universe this does not mean, however, that you are aware of everything that exists. In fact, you are consciously aware of only a relatively narrow range of perceptions. You perceive certain perceptions and not others. Other monads may perceive perceptions that you do not, or you may (as Leibniz makes clear in the quotes above) have perceptions related to those of other monads, though from a different and unique point of view.
3. Windowless Monads in the City of God
I stated earlier that each monad re-presents the perceptions of all the other monads. This has the potential to be misunderstood as meaning that, for example, I am experiencing other monads and their perceptions; in other words, my perceptions have as their object something external to me, just not an “external world” of physical objects. This is not what Leibniz means, however. It is rather that the “representation” within each monad is a duplication of the world of perceptions experienced by all the other monads — but, again, from a unique point of view. Leibniz is at great pains to make clear to us that nothing enters monads from outside of them:
[Nothing] ever enters into our mind naturally from the outside; and we have a bad habit of thinking of our soul as if it received certain species as messengers and as if it has doors and windows. We have all these forms in our mind; we even have forms from all time, for the mind always expresses all its future thoughts and already thinks confusedly about everything it will ever think about distinctly. And nothing can be taught to us whose idea we do not already have in our mind, an idea which is like the matter of which that thought is formed.  
In the Monadology, Leibniz famously writes “The monads have no windows through which something can enter or leave.”   (This has given rise to the expression “windowless monads.”) Thus, Leibniz describes all of our perceptions as phenomenal (a term taken up by Kant, with whom it is most famously associated). In other words, our perceptions are not perceptions of something existing in itself, outside our monad. As I noted earlier, this does not mean that Leibniz denies the world; rather, the world just is our perceptions. But someone might object (indeed, many might object) that this makes the world something completely “subjective.” Doesn’t Leibniz confine us entirely to a “world” of subjective impressions? Isn’t it possible that each monad might experience an entirely different world? Worse yet, how do we even know that we are not entirely alone, dreaming the dream of a world? Leibniz’s answer to these problems is to bring God into his philosophy, as — so critics might say — a kind of deus ex machina to extricate himself from the threat of solipsism.  
I will pass over, in the interests of time, Leibniz’s arguments for God’s existence, which are no more convincing than those offered by Descartes and other rationalists. Instead, we will content ourselves with a description of the role played by God in Leibniz’s philosophy. God, Leibniz argues, is a kind of super-monad who coordinates the perceptions of all the countless finite monads so that they have the consistent experience of living in the exact same universe, though seen from a multitude of perspectives. “God alone (from whom all individuals [i.e., monads] emanate continually and who sees the universe not only as they see it but also entirely differently from all of them) is the cause of this correspondence of their phenomena and makes that which is particular to one of them public to all of them; otherwise, there would be no interconnection.”  
Thus, although the monads receive no perceptual “input” from outside of them, and though they do not act upon each other (see Monadology, 51) they are nevertheless acted upon by God: “[There] is no external cause acting on us except God alone, and he alone communicates himself to us immediately in virtue of our continual dependence.”   Presumably, we are supposed to understand that God is the author of the phenomenal universe each monad perceives in its own way. Leibniz draws from this a fascinating and unexpected conclusion:
Thus we have ideas of everything in our soul only by virtue of God’s continual action on us, that is to say, because every effect expresses its cause, and thus the essence of our soul is a certain expression, imitation or image of the divine essence, thought, and will, and of all the ideas comprised in it. It can then be said that God is our immediate external object and that we see all things by him. For example, when we see the sun and the stars, it is God who has given them to us and who conserves the ideas of them in us, and it is God who determines us really to think of them by his ordinary concourse while our senses are disposed in a certain manner, according to the laws he has established. God is the sun and the light of souls, the light that lights every man that comes into this world [John 1:9], and this is not an opinion new to our times.  
(Leibniz goes on to argue that his conclusion agrees with “Holy Scripture and the Church Fathers.”) Thus, in every perception it is actually God that we are perceiving. The universe is an expression of God and God has caused us to perceive him as the universe; when we perceive the sun and the stars, for example, it is God that is our actual object. However, it is not just the universe that is an image of God. “Minds,” Leibniz avers, “are also images of the divinity itself, or of the author of nature, capable of knowing the system of the universe, and imitating something of it through their schematic representations of it, each mind being like a little divinity in its own realm.”   Here no argument is necessary to establish that Leibniz’s position agrees with scripture, as the agreement is so obvious: “Let us make man in our image, after our likeness” (Genesis 1:26).
In elaborating the relationship between God and the monads, Leibniz draws upon an image from Augustine in order to make another remarkable claim: “From this it is easy to conclude that the collection of all minds must make up the city of God, that is, the most perfect possible state under the most perfect of monarchs.”   God, he says elsewhere, is “the monarch of the most perfect republic, composed of all minds, and the happiness of this city of God is his principal purpose.”   Augustine, in The City of God (written early fifth century) had distinguished between the city of God and the “earthly city.” The latter is made up of individuals who are preoccupied with the cares and pleasures of the world. The former is populated by those who have abjured those pleasures in order to dedicate themselves to religious piety. In words that will have far-reaching consequences for later German philosophy, Leibniz adapts this distinction as follows: “This city of God, this truly universal monarchy, is a moral world within the natural world, and the highest and most divine of God’s works.”  
While the actions of moral individuals may sometimes seem to have no effect in the perceptible world, and may even result in suffering (while the immoral seem to flourish), it is God’s task, as monarch of his perfect republic, to see that everything works out in the end. “Under this perfect government,” Leibniz writes,
there will be no good action that is unrewarded, no bad action that goes unpunished, and everything must result in the well-being of the good, that is, of those who are not dissatisfied in this great state, those who trust in providence, after having done their duty, and who love and imitate the author of all good, as they should, finding pleasure in the consideration of his perfections according to the nature of genuinely pure love, which takes pleasure in the happiness of the beloved. This is what causes wise and virtuous persons to work for all that appears to be in conformity with the presumptive or antecedent divine will, and nevertheless, to content themselves with what God brings about by his secret, consequent, or decisive will, since they recognize that if we could understand the order of the universe well enough, we would find that it surpasses all the wishes of the wisest, and that it is impossible to make it better than it is.  
While, as I have noted, we may not always perceive that justice has been done in this perceptible world, Leibniz does believe that the perceptible universe improves over time: “Now, the efficacy [vertu] a particular substance has is to express well the glory of God, and it is by doing this that it is less limited. And whenever something exercises its efficacy or power, that is, when it acts, it improves and extends itself insofar as it acts.”   As Klein notes, “The world as a whole, therefore, tends to progress.”  
4. Leibniz and the History of Philosophy
We may close out this survey of Leibniz’s metaphysics by considering how the philosopher himself understands the place of his system in the history of ideas. This is no insignificant matter. We have already seen that Leibniz is concerned to argue that his philosophy agrees with scripture. The very last section of the Discourse on Metaphysics is titled “Jesus Christ Has Revealed to Men the Mystery and Admirable Laws of the Kingdom of Heaven and the Greatness of the Supreme Happiness That God Prepares for Those Who Love Him.”   What Leibniz really means here is that scripture offers to mankind the same system of ideas Leibniz presents in his philosophy, only in the form of religious revelation.
Leibniz was familiar with Agostino Steuco’s De perenni philosophia (1540) which attempted to argue that the ideas of the sages and philosophers of classical antiquity were in fundamental agreement with Christian teachings. Leibniz borrows the term “perennial philosophy” and argues that his philosophy is an expression of it — that, as Klein puts it, “his system preserves and unites the thoughts of all preceding generations about man, universe, and God.”   At one point in the Discourse, for example, Leibniz defends the Scholastics against their modern detractors, saying, like the archetypal modern that he was, “I am even convinced that, if some exact and thoughtful mind took the trouble to clarify and summarize their thoughts after the manner of the analytic geometers, he would find there a great treasure of extremely important and wholly demonstrative truths.”  
Of course, how we evaluate Leibniz’s place in the history of ideas will inevitably be quite different from the philosopher’s own evaluation. While the influence of Greek philosophy and Scholasticism on Leibniz is fascinating, what is most interesting about his thought are the seeds of future ideas that it sows. Here we can really see why Heidegger credits Leibniz with being such a pivotal figure. Although a great deal could be said, I will note seven major themes that are developed in later German philosophy:
1. The theory of the phenomenality of objects. As already noted, Kant (who was early on a follower of Leibniz and Christian Wolff’s “systematization” of him) borrows this idea from Leibniz. To say that objects are phenomena, for Kant, means that we only know them as they appear to us. Kant opposes phenomena to “things as they are in themselves”; things as they are independently of how they appear to us, which we can never know. The basis for this distinction exists in Leibniz, where the phenomenal universe stands opposed to the “metaphysical world” beyond experience, consisting in monads, their relations, and their relationship to God. The difference is that Leibniz believed that that metaphysical world was knowable, by means of the “pure reason” that Kant critiques.
2. Intersubjective agreement. Recall that Leibniz says that “God alone . . . is the cause of this correspondence of [the monads’] phenomena and makes that which is particular to one of them public to all of them; otherwise, there would be no interconnection.” In other words, the objectivity of the monads’ perceptions is not due to their correspondence with external objects, but rather to their agreement with each other (an agreement brought about by God). This idea was an important influence on Kant (though he does not attribute intersubjective agreement to God, but rather to the possession of common a priori cognitive structures).
3. The idea that God is “our immediate object”; that in experiencing phenomena we are actually perceiving God. This intriguing idea will blossom into the Hegelian conviction that since all objects derive their Being from their place within the whole, within the Absolute (in religious language, God), in knowing any given being we are (implicitly) knowing the whole. Arguably, Leibniz likely derives his idea from Spinoza, whom he met and with whose ideas he was conversant. Spinoza was also a significant influence on Hegel.
4. The idea that there is “a moral world within the natural world.” This has borne much fruit in later philosophy:
(a) We see its influence in Kant’s conviction that we live simultaneously in two “worlds.” The phenomenal world, which can be thoroughly studied by science, gives no evidence that we are free, which is a necessary condition of being moral (actions are only moral if freely chosen). Yet we have the conviction of being governed by moral laws that command us to act in various ways. Thus, Kant argues, while the phenomenal world gives no evidence of freedom, we are compelled to believe that beyond the phenomena (in the “world” of things as they are in themselves) we are nonetheless free.
(b) Leibniz’s characterization of the moral world as the “city of God” also influenced Kant’s idea of the “kingdom of ends.” Kant held that, as moral actors, we must regard ourselves as willing laws binding on all other rational beings. This leads him to speak of a “systematic union of different rational beings under common laws,” or a “Kingdom of Ends.” This formulation of Kant’s “categorical imperative” requires us to conform our acts to the laws of a hypothetical moral republic. The difference from Leibniz is that, for Kant, each man is the legislator and must will the laws himself. God has been deposed and a genuine republic has been created. (Giving new meaning to Huey Long’s slogan, “Every man a king.”)
(c) In Kant’s successor, the idealist J. G. Fichte (1762–1814), the juxtaposition of the “moral world within the natural world” becomes radicalized. Fichte holds that it is the vocation of man to overcome the natural world and to remake it in the image of the moral ideal. Fichte is, in a great many ways, the quintessential modern philosopher, and we will return to him in a later essay. Strangely, he is neglected by Heidegger, who should have seen him as much grist for his mill.
5. Leibniz’s conviction that God brings about justice, even if we do not perceive this in the phenomenal world. Kant will argue that this idea is a “necessary postulate” of the moral consciousness. In other words, though it is impossible to prove that God sees to it that good people are rewarded and bad people punished (or even, for that matter, to prove that God exists at all) we nevertheless must believe in a notion of cosmic justice, else we might abandon moral action as a result of all the injustice we witness in this life. Or, as Leibniz himself puts the matter: “This [belief] is what causes wise and virtuous persons to work for all that appears to be in conformity with the presumptive or antecedent divine will, and nevertheless, to content themselves with what God brings about by his secret, consequent, or decisive will.”
6. Christianity as a religious expression of philosophical truth. This idea is most famously developed by Hegel, who argues that religion in general, but Christianity in particular, expresses philosophical truths in the form of “picture-thinking” (Vorstellung). Thus, for example, religion speaks of “God,” philosophy of “the Absolute”; religion speaks of the “Trinity,” Father, Son, and Holy Spirit, Hegelian philosophy of Logic, Nature, and Spirit, etc.
7. The perennial philosophy. This is also an idea famously developed by Hegel, whose system purports to weave together and reconcile all previous philosophy. In an early essay, Hegel wrote that “there has been only one and the same philosophy at all times. So not only am I promising nothing new here, but rather am I devoting my philosophical efforts precisely to the restoration of the oldest of old things, and on freeing it from the misunderstanding in which the recent times of unphilosophy have buried it.”
While all the above is fascinating, we must now turn to Heidegger’s specific arguments for why Leibniz “prepares the completion of modern metaphysics.” His account hinges on a problem concerning the phenomenality of perception, one that Leibniz himself addresses. At first glance, this will seem almost like minutiae — like one of those “technical” questions philosophers raise that often produce eye-rolling even from gifted intellects. For Heidegger, however, Leibniz’s answer to this question is of signal importance for the history of metaphysics.
5. Conclusion: Conatus and Will-To-Power
As we have seen, all perception for Leibniz is phenomenal — perceptions do not correspond to or re-present external objects. The world is just the world of our perceptions. Now, Leibniz feels that the acceptance of this doctrine should not change the daily conduct of our lives at all. He believes that he is simply giving an account of our experience that differs from that offered by what passes for “common sense.” Indeed, he believes that his account describes our actual experience perfectly well. However, one might express skepticism about this. For example, one might say “when I go about my daily life it certainly seems to me that I am moving through a physical world existing outside my perceptions. For example, when I turn a corner on a city street there is a change in scenery. I attribute this to the fact that I have physically moved to a different part of a physical location, which is physically different from the earlier part. If you reject this possibility, what explains how my perceptions change when I (seem to) turn that corner?”
Leibniz’s answer appeals to what he calls appetition: “The action of the internal principle which brings about the change or passage from one perception to another can be called appetition; it is true that the appetite cannot always completely reach the whole perception toward which it tends, but it always obtains something of it, and reaches new perceptions.”   In other words, what causes the change from one perception to another is not physical change, but is rather the result of the subject’s appetite. So, what does Leibniz mean by this? That perceivers have an appetite for more perceptions and that that causes us to move (phenomenally) beyond one perception to the next perception, and on to the next, and so on and so forth? Yes, this is exactly what he means. Perception and appetition are bound up with each other.
In one essay, Leibniz writes that “The idea of energy or virtue, called by the Germans Kraft and by the French la force, and for the explanation of which I have designed a special science of dynamics, adds much to the understanding of the notion of substance.”   Recall that all substances, all monads, are in act. This act, as we have discussed, is perception. But we can easily see that perception may be understood as expressing a certain drive or energy. The perceiver is hungry to perceive; to perceive more and more; to move from one perception to the next. It is with good reason that Leibniz links perception with appetite.
Leibniz also uses the term conatus to refer to appetition. This is the perfect active participle of Latin cōnor, meaning “to attempt” or “to try.” Conatus is therefore a “trying,” but it is better translated as “drive.” For Leibniz, the conatus is a will towards action, which will realize its aim unless it is somehow constrained. Leibniz seems to derive this term from Spinoza, with whom it is more famously associated. For Spinoza, conatus is the tendency or power of a thing to persist in its own being. Unless hindered, not only will everything succeed in doing this — everything will also tend to try and maximize its own power. For Leibniz, this will to power is bound up with perception itself.
Indeed, Heidegger argues that, for Leibniz, the two are practically indistinguishable: “The simple self-containedness of what is truly persistent . . . consists in representing as striving. Perceptio and appetitus are not two determinations of the reality of what is real which are first produced. Rather their essential unity constitutes the simplicity of what is truly one, and thus its unity and its beingness.”   Although Heidegger’s language is far from clear, his point seems to be that the unity of the monad requires the unity of representing and striving. We have already seen that, for Leibniz, Being or substance just is the mind in its act of perceiving. And we have now taken a further step, in seeing that this perceiving is inherently appetitive; it is a drive for power. Thus, Being for Leibniz = perceptio–appetitus. Or, Being is the unity of perception/representation and will.
At the beginning of this essay, we saw that Heidegger credits Leibniz with the preparation of the completion of modern metaphysics. The actual completion, on the other hand, is carried out by Nietzsche. So how does Leibniz prepare the way for Nietzsche? The answer may now be obvious to the reader, but Heidegger explains it in unusually clear language:
[For] the modern history of metaphysics, the name subjectivity expresses the full essence of Being only when Being’s character of representation is not thought about simply or even predominantly, but rather when appetitus and its developments as a fundamental characteristic of Being have become evident. Ever since the developed beginning of modern metaphysics, Being is will, that is, exigentia essentiae [literally, “drive to exist”]. “Will” contains a manifoldness of essence. It is the will of reason or the will of spirit, it is the will of love or the will to power.  
As one Heidegger commentator puts matters,
It was Leibniz who carried out the “decisive beginning” of the metaphysics of subjectivity . . . by his doctrine of “monads” as subjects who strive to actualize all their experiences. By introducing an Aristotelean dynamism into Descartes’s static metaphysics of the subject, Leibniz opened the way for Nietzsche’s doctrine that the Will to Power constitutes the being of all entities. . . . [Monads] were self-willing agents which actualized and made present all the entities in their experience. Leibniz still maintained that monads were created by God, but it was not a great step from Leibniz to the doctrine which Heidegger attributed to Nietzsche: that everything we experience is merely the product of human will.  
(Just why Nietzsche’s doctrine of will-to-power “completes” metaphysics will be dealt with in a later essay in this series.)
We noted in the last installment  that it is in the modern period that the idea of “systems” of knowledge begins to proliferate. Leibniz’s philosophy serves as a paradigm example of such systems. Indeed, he sets the standard for all “systematic philosophy” to come, and all later systematizers — men like Wolff, Kant, Fichte, Reinhold, Schelling, Novalis, Hegel, and even Schopenhauer — are, to one degree or another “Leibnizians” in their conception of what constitutes a “philosophical system.” Leibniz’s philosophy may also be said to be a paradigm case of what Heidegger calls the ideal of the “world picture,” discussed extensively in the last essay.
In “The Age of the World Picture,” Heidegger remarks that “The uniqueness of the systematic of Leibniz, Kant, Fichte, Hegel, and Schelling — a systematic that is inherently diverse — has still not been understood.”   In The End of Philosophy, Heidegger sheds a bit more light on that “systematic”:
The system, thought as the unity of order of knowledge, appears at first to be merely the paradigm of portrayal for everything knowable in its structure. But because Being as reality is itself will, and will is the unification of the unity of totality striving for itself, the system is no mere schematic order which the thinker has in mind and always presents only incompletely and each time somehow one-sidedly. The system, the Sustasis, is the essential structure of the reality of what is real — of course, only when reality has been discovered in its essence as will. This happens when truth has become certainty, evoking from the essence of Being the fundamental characteristic of the universal ensurance of structure in a ground which ensures itself.  
What Heidegger means is that the idea of systems of knowledge or of philosophy could only arise when Being itself had been understood as will.   Note that he says that “will is the unification of the unity of totality striving for itself.” The modern subject’s will to total knowledge, its desire to make all beings permanently present (its “metaphysics of presence”) causes it to conceive of reality as in fact totalizable or unifiable. In other words, because it wants to attain the “world picture,” to gain knowledge of reality conceived as a total system, it projects this “systematic” character onto the world itself. The will to arrive at the total system of knowledge of what is is only possible if what is is itself conceived as a total system.
This idea is so engrained in us (mainly due to its role in modern science as a regulative principle) we now have trouble imagining how it could be otherwise. How could the universe not be a total system, knowable in its systematic order by man? But suppose that this is, in fact, wildly wrong. Suppose that the universe is a lot “messier” than we think it is. Suppose all things do not “hang together” or cohere in a way that is conducive to understanding. Suppose that there is contradiction, spontaneity, unpredictability, and mystery woven into the fabric of existence itself. Such a possibility is, for the mind of a man like Leibniz, completely unthinkable. Indeed, it is unthinkable — and that is the point.
To be continued . . .
* * *
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  Jacob Klein, “Leibniz, an Introduction,” in Jacob Klein: Lectures and Essays, ed. Robert B. Williamson and Elliott Zuckerman (Annapolis: St. John’s College, 1985), 212.
  Martin Heidegger, The End of Philosophy, trans. Joan Stambaugh (New York: Harper and Row, 1973), 31.
  Klein, 202. See Frederick Copleston, A History of Philosophy, Vol. IV: Descartes to Leibniz (New York: Image Books, 1985), 297.
  See, for example, Monadology 8-9 (reference to the Monadology is by paragraph number). I am using this edition: G. W. Leibniz, Discourse on Metaphysics and Other Essays, trans. Daniel Garber and Roger Ariew (Indianapolis, Indiana: Hackett Publishing, 1991).
  Though Leibniz uses the language of “infinity,” he really means that the number of substances is so great it would be impossible to count them all.
  See, for example, Monadology 19-23.
  Klein, 204. Italics in original.
  Discourse on Metaphysics, in G. W. Leibniz, Discourse on Metaphysics and Other Essays, trans. Daniel Garber and Roger Ariew (Indianapolis, Indiana: Hackett Publishing, 1991), 9. Reference is by page number.
  Discourse, 17.
  Monadology, 56-57. Heidegger also quotes a letter by Leibniz in which he says, “Every simple substance is by its nature (if one may say so) a concentration and a living mirror of the whole universe, according to its point of view.” End of Philosophy, 36.
  Discourse, 28.
  Monadology, 7.
  Solipsism is the theory that only I exist, or all that exists is my mind. No philosopher has ever argued for such a position, for to whom could they direct their arguments? Instead, solipsism is regarded as a problem to be avoided at all costs.
  Discourse, 15.
  Discourse, 30.
  Discourse, 30. Italics added.
  Monadology, 83.
  Monadology, 85.
  Discourse, 39.
  Monadology, 86.
  Discourse, 81.
  Discourse, 16.
  Klein, 214.
  Discourse, 40.
  Klein, 212.
  Discourse, 11.
  Monadology, 15.
  From On the Reform of Metaphysics and the Notion of Substance. Quoted in Copleston, 298.
  End of Philosophy, 37.
  End of Philosophy, 47.
  Michael E. Zimmerman, Heidegger’s Confrontation with Modernity (Bloomington, Indiana: Indian University Press, 1990), 172.
  Martin Heidegger, Off the Beaten Track, trans. Julian Young and Kenneth Haynes (Cambridge University Press, 2002), 76.
  End of Philosophy, 48-49.
  In the passage that follows the one just quoted, Heidegger writes, “Because veritas does not yet ground its essence in the certitudo of the cogitare in the medieval period, Being can never be systematic. What is called a medieval system is always just summa as the presentation of the whole of doctrine. But the idea of a system is still less commensurate with the philosophy of Plato and Aristotle.” End of Philosophy, 49.