In 1690, Gottfried Wilhelm Leibniz wrote to Thomas Burnett that he had encountered, rather late, the work of Anne Conway — and that he found it “largely in accordance” with his own philosophy. He called her a “Cartesian lady” of remarkable ability. He did not dwell on the fact that her Principles of the Most Ancient and Modern Philosophy, probably composed in the later 1670s and circulated in manuscript before its posthumous Latin publication in 1690, followed by an English edition in 1692, contained ideas with striking affinities to themes later associated with his mature monadology.
This is not a small coincidence. It is one of the most consequential and contested questions of intellectual debt in the history of Western philosophy — and it has been allowed to stand for three centuries because Conway was a woman who never published in her own lifetime, whose work circulated through intermediaries, and whose name was easy to fold into the footnotes.
Who Anne Conway Was
Anne Conway (1631–1679) was born Anne Finch in London, the daughter of Sir Heneage Finch. She was largely self-educated in philosophy — barred from Cambridge as a woman — but corresponded extensively with Henry More, the Cambridge Platonist, who became her tutor by letter. She read Descartes, Hobbes, Spinoza, and Kabbalah. She converted to Quakerism in the last years of her life, a move that is philosophically significant rather than merely biographical: her metaphysics demanded it.
She suffered from debilitating migraines for most of her adult life, migraines so severe that they have been described by her contemporaries in terms that suggest cluster headaches or a neurological condition of extraordinary cruelty. She conducted her philosophical work in intervals between pain. Her Principles was written in those intervals, revised, and left unfinished. It was translated from English into Latin by her friend Francis Mercury van Helmont, and it was van Helmont who brought it — and her ideas — into direct contact with Leibniz.
The Substance of the Overlap
The similarities between Conway’s Principles and Leibniz’s Monadology (1714) are not superficial. They concern the deep structure of reality.
Conway argued that all created substances are composed of infinitely divisible monads — she uses the term — each of which is a living, perceiving unit. These monads are not inert matter; they are animated by spirit, and the distinction between matter and spirit is one of degree rather than kind. All created things exist on a continuum of vitality, from the most sluggish matter to the most refined spirit. God alone stands outside this continuum as the uncreated source.
This overlaps in important respects with the Leibnizian picture. Leibniz’s monads are windowless, perceiving, non-extended units that constitute all reality. His pre-established harmony replaces Conway’s more direct account of how monads interact, but the ontological furniture is strikingly similar. Both thinkers rejected Cartesian dualism — the hard split between res cogitans and res extensa — on the grounds that it made mind-body interaction inexplicable. Both proposed instead a vitalist, graduated metaphysics in which perception is a universal feature of substance.
Conway articulated this related position before Leibniz’s mature monadological writings, in a manuscript that Leibniz’s close associate van Helmont carried directly to him.
What Leibniz Said and Didn’t Say
Leibniz’s acknowledgment of Conway is technically present in the historical record. He mentions her. He calls her work consonant with his. But “consonant with” is doing a great deal of work in that sentence. It implies two independent thinkers who happened to agree, rather than leaving open the possibility that one thinker encountered a prior framework and incorporated parts of it into his own developing system.
The more precise question — one that historians of philosophy have continued to debate — is how Leibniz’s monadology as a systematic doctrine relates to his exposure to Conway’s manuscript through van Helmont. The chronology is uncomfortable, but not simple. Leibniz had already developed important parts of his substance metaphysics before 1690, notably in the Discourse on Metaphysics and in his correspondence with Arnauld in the mid-1680s. Van Helmont and Leibniz were in close contact through the 1690s. The Principles was published in Latin in 1690. Leibniz’s mature monadological writings come after this. His 1695 New System of Nature is often identified as an important public stage in his substance metaphysics, but not as the monad doctrine in its full mature form.
None of this proves deliberate appropriation. Intellectual history rarely yields that kind of smoking gun. What it does establish is that the standard story — Leibniz as the sole originator of monadological metaphysics — is, at minimum, incomplete.
The Vitalism That Got Domesticated
There is also a philosophical difference between Conway and Leibniz that deserves attention, because it reveals what may be lost when related ideas are set inside a more academically respectable framework.
Conway’s vitalism is radical. For her, the continuum between matter and spirit is not merely a metaphysical convenience; it is a moral and theological claim. Because all created things are animated and capable of development, all created things are capable of redemption. Her metaphysics underwrites a form of universal salvation — a position she shared with her Quaker contemporaries — and it extends moral consideration to animals and to matter itself in a way that is genuinely unusual for the period.
Leibniz’s monadology domesticates this. His monads are windowless — they do not interact, they do not form a genuine continuum of development, and his system is ultimately more compatible with orthodox Christian hierarchy than Conway’s. The radical implications of a truly vitalist, graduated metaphysics — implications Conway drew explicitly — are softened into a more palatable rationalist system.
This is not incidental. It is what can happen when a woman’s heterodox ideas are read through a man’s more institutionally secure framework. The structure survives; the radicalism is edited out.
The Marginalia Problem
Conway’s Principles survives in a relatively small number of copies. The manuscript history is complex, filtered through van Helmont’s translation and editorial choices. We cannot be entirely certain that what we have is precisely what Conway wrote, in the order she intended, with the emphases she would have chosen.
This is the marginalia problem in its most acute form: women philosophers of the early modern period often exist in the record as mediated texts, translated and transmitted by men who had their own agendas, their own theological commitments, their own reasons for presenting ideas in particular ways. Van Helmont was a sincere admirer of Conway, but he was also a strange and syncretic thinker whose own views inflect the Principles as we have it.
What we can say with confidence is that the Principles represents a systematic, original, and sophisticated metaphysical position — not a set of intuitions, not a devotional exercise, not a commentary on male philosophers. It is a primary philosophical text, and it has been treated as a curiosity.
Why It Matters Now
The recovery of Anne Conway is not an exercise in historical sentimentality. It matters philosophically because the monadological tradition looks different when you see its full genealogy. The questions Conway was asking — about the relationship between matter and mind, about the moral status of non-human creatures, about whether a metaphysics of pure mechanism can account for life — are questions that remain live. Her answers, unmediated by Leibniz’s rationalizing framework, are in some respects more interesting than the canonical version.
Her insistence that matter and spirit differ in degree rather than kind anticipates debates in philosophy of mind that we are still having. Her moral extensionism — the view that the continuum of vitality grounds a continuum of moral consideration — is more ecologically sophisticated than anything Descartes or Leibniz produced. Her rejection of Cartesian dualism was arrived at independently and argued on grounds that are, in places, more compelling than the arguments Leibniz deployed.
She deserves to be read as a philosopher, not as a precursor. The Principles should be on syllabi not because it is a historical curiosity or because Conway was a woman who managed to think despite her circumstances, but because it is a genuinely good piece of metaphysics that the tradition has misfiled.
Leibniz got the canonical credit. Conway got a footnote. The argument for correcting that arrangement is not primarily about justice — though it is also about justice — it is about getting the history of philosophy right.
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