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The Philosopher’s Plant 7.0: Leibniz’s Blades of Grass

The year: 1685. The place: the gardens of Herrenhausen, the Electoral Palace of Princess Sophie in Hanover.

A frantic search is under way, led by the distinguished courtier Carl August von Alvensleben. No, the ladies and gentlemen of the Hanover court were not looking for a lost earing of Princess Sophie. The object of their quest was much more prosaic than that; they tried to find two leaves that would be exactly alike. Why this sudden obsession with the plants growing in an undeniably magnificent Baroque garden, the most emblematic of its kind in Europe?

The answer thrusts us into the thicket of Gottfried Wilhelm Leibniz’s philosophy and introduces one of its pivotal principles, which von Alvensleben attempted to refute in the crudest empirical way imaginable.

Fast forward to June 2, 1716. In a letter addressed to English philosopher Samuel Clarke, Leibniz recalls the garden episode in connection to his famous principle of the identity of indiscernibles, or, simply put, “Leibniz Law”:

There is no such thing as two individuals indiscernible from each other. An ingenious gentleman of my acquaintance, discoursing with me in the presence of Her Electoral Highness, the Princess Sophia, in the garden of Herrenhausen, thought that he could find two leaves perfectly alike. The princess defied him to do it, and he ran all over the garden a long time to look for some; but it was to no purpose. (1)

The futile search casts in the limelight a metaphysical principle that extends to the least element of nature, such as green leaves or, as we shall see, blades of grass. If no two entities are exactly the same in all respects, then they all bear a mark of uniqueness and individuality, ultimately harkening back to the wisdom of the Creator.

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Since God does not do anything randomly, but always for a sufficient reason and following the laws He instituted, there would be no point for Him to place two exactly identical beings in different places. Each being and every corner of the material world are matchless and irreplaceable. The ethical consequences of this ontological axiom are conspicuously manifest: to destroy a leaf, let alone an entire plant, is to do away with something that will not regrow in exactly the same shape ever again. Although Leibniz will stop short of drawing this implication of his basic principle, it is safe to say that never has a metaphysical intuition been as conducive to ethical reasoning and practice as that pertaining to the identity of indiscernibles.

The incident at the royal gardens became notorious in the history of philosophy. In his Logic, Hegel noted how ironic the search for an empirical counter-proof to a metaphysical law of difference was: “As regards the principle of Leibniz, difference must be understood to mean not an external and indifferent diversity merely, but difference essential. Hence the very nature of things implies that they must be different.” (2) Regardless of the time one dedicates to a study of concrete leaves or blades of grass, with all their finite differences, one will never get to the bottom of the issue, namely to “difference essential,” one that makes things what they are, bestowing identity upon them.

A garden-variety of metaphysics, which of necessity isolates difference and identity from the examples of these concepts we find in our life-world, comes to a head with and mocks the forgetting of metaphysics in the royal garden. The diversity of leaves and blades of grass is “external and indifferent” — hence, insignificant when inspected from the heights of metaphysics. Actual differences are but effects of the intangible wellspring of things.

But, if real distinctions and the unique traits of plants do not matter, then the ethical implications of Leibniz’s Law are also nullified, as the destruction of an empirically unique tree does not affect in the least that difference which Hegel calls “essential.” The return of metaphysics clashes with the ethics oriented toward the finite in its finitude.

Perhaps, neither von Alvensleben nor Hegel got Leibniz right, because for the latter, discernment and indiscernibility are neither purely empirical nor absolutely metaphysical categories. The differences among living beings of the same kind are not the ontological be-all and end-all, and even less so are they something entirely external. Rather, they stand for the differences within God, expressing an infinite number of His perspectives on the world.

If there are many species of plants and if each species includes an untold number of subspecies, it is because all these must exist so as to actualize the immense possibilities of God’s self-expression. The brute fact of biodiversity and a mindboggling empirical variation within a given species are awash with theological and ethical underpinnings. The apparently neutral statement, to the effect that any two leaves growing on the same bush are materially distinct, means that their actual differences, far from being “external and indifferent,” contribute to the fullest (and best) possible actualization of divine essence in existence.

A year after the garden episode, Leibniz revisits the identity of indiscernibles in an essay appropriately titled “Primary Truths.” Divulging that the source of this principle is St. Thomas’s “separated intelligences,” “which, he [St. Thomas] said, never differ by number alone,” he contends that the same is true for any and all material objects: “[N]ever do we find two eggs or two leaves or two blades of grass in a garden that are perfectly similar. And thus, perfect similarity is found only in incomplete and abstract notions…” (3)

Why did blades of grass merit inclusion as examples of Leibniz’s principle? Perhaps the etymology of his family name holds the key.

A derivative of the Slavic lipnice, “Leibniz” is evocative of “a certain kind of grass that grows in river bottoms.” (4) In the very first blog post, we have seen how Plato inscribed his proper name in the plane tree that overshadows Phaedrus. It was also not uncommon for thinkers of the early modern period to encrypt their proper names in their philosophical writings. Spinoza finishes his Ethics with the praise of blessedness, beatitudo — Proposition 42: “Blessedness is not the reward of virtue, but virtue itself…”(5) — which is pertinent to the translation both of his Hebrew (Baruch) and his Latin (Benedictus) names, meaning “blessed.” For Spinoza to say, then, that blessedness is virtue itself is an act of self-affirmation, consistent with his thinking.

So, what is Leibniz’s purpose in adding blades of grass to a list of examples of the law that has become associated with his name? Is it not to assert, whether consciously or not, his own individuality and uniqueness, arguing, to a large extent contra Spinoza, that we are not a series of interchangeable avatars of the one substance?


(1) G.W. Leibniz & Samuel Clarke, Leibniz and Clarke: Correspondence, edited by Roger Ariew (Indianapolis & Cambridge: Hackett, 2000), p. 22.
(2) G.W.F. Hegel, Logic: Encyclopedia of the Philosophical Sciences, Part II, translated by William Wallace (Oxford: Oxford University Press, 1975), p. 170.
(3) G.W. Leibniz, Philosophical Essays, edited by Roger Ariew & Daniel Garber (Indianapolis & Cambridge: Hackett, 1989), p. 32.
(4) Benson Mates, The Philosophy of Leibniz: Metaphysics and Language (Oxford: Oxford University Press, 1989), p. 17, FN. 16.
(5) Baruch Spinoza, Ethics, translated by Edwin Curley (London & New York: Penguin Classics, 2005), p. 180.