Professor Stewart Duncan has assembled a helpful outline of Cavendish’s Philosophical Letters (1664), which he originally posted and continues to update on his website. This is a valuable scholarly resource for approaching a text in which Cavendish maps out her philosophy’s engagement with and reaction against the ideas of Hobbes, Descartes, Henry More, van Helmont, and other seventeenth-century philosophers. Professor Duncan’s website also features modernized selections from Philosophical Letters for use in the classroom.

Letters in the Philosophical Letters

This document gives some information about the letters that make up Margaret Cavendish’s Philosophical Letters (London, 1664). The descriptions of each letter are in a small number of categories: number, topic, reference, and note.

Number: I have numbered all the letters by section and letter. Thus, for example, 2.12 is letter 12 of section 2. Section 1 of the Philosophical Letters largely engages with Hobbes and Descartes, section 2 with More, and section 3 with J.B. van Helmont. Section 4 then engages with a variety of other figures.

Topic: I have written a (very) short description of the topic of each letter.

Reference: These descriptions of texts referred to are largely the ones that Cavendish herself gives in the text of the Philosophical Letters. In other places, where Cavendish’s references are cryptic or incomplete, I have tried to fill them out. Bibliographical details are provided in a references section at the end of the document. References to other books use the internal divisions (e.g., chapters, sections) of those books, unless the references explicitly specify that page numbers are being used.

Note: I use this for all other content, of which there is not much. Occasionally Cavendish refers to someone she has talked to. If I could identify them, that information would be here. Outstanding questions about identification of authors are also noted here.

Recent updates: minor additions to entries in Part 1 in March and April 2014

A preface to the reader

Reference: Du Verger (1657)
Note: Cavendish comments briefly on a work criticizing passages in her World’s Olio on monastical life. Although Sarasohn (2010, 127 n.4) claims that the work has not survived, I suggest following Narramore (2013) that it is Du Verger’s short book.

Section 1. Hobbes and Descartes

Number: 1.1
Topic: Introductory

Number: 1.2
Topic: The infinity of matter; a defence of aspects of Cavendish’s view
Reference: The creation story of Genesis 1, and the Nicene Creed

Number: 1.3
Topic: The eternity of nature; a defence of aspects of Cavendish’s view

Number: 1.4
Topic: Hobbes on the cause of perception
Reference: Leviathan 1

Number: 1.5
Topic: Hobbes on something like inertia and on decaying sense; perception again; natural and artificial motion
Reference: Leviathan 2

Number: 1.6
Topic: Hobbes on imagination
Reference: Leviathan 2

Number: 1.7
Topic: Hobbes on dreams
Reference: Leviathan 2

Number: 1.8
Topic: Hobbes on imagination again
Reference: Leviathan 2-3

Number: 1.9
Topic: Hobbes on language and reason
Reference: Leviathan 4-5

Number: 1.10
Topic: Hobbes on understanding and reason, and the reason of animals
Reference: Leviathan 4

Number: 1.11
Topic: Hobbes on children’s reason
Reference: Leviathan 4

Number: 1.12
Topic: Hobbes on animals and animal motion
Reference: Leviathan 6

Number: 1.13
Topic: Hobbes’s politics avoided
Reference: The rest of Leviathan

Number: 1.14
Topic: Hobbes on the geographic distribution of philosophy, and Cavendish on the two souls
Reference: De Corpore 1.7

Number: 1.15
Topic: Hobbes on infinity
Reference: De Corpore 7.12

Number: 1.16
Topic: Hobbes on accidents
Reference: De Corpore 8

Number: 1.17
Topic: Hobbes on place and magnitude
Reference: De Corpore 8

Number: 1.18
Topic: Hobbes on sense and animal motion in De Corpore
Reference: De Corpore 25

Number: 1.19
Topic: Hobbes on light, heat, and colours
Reference: De Corpore 27

Number: 1.20
Topic: Light, again

Number: 1.21
Topic: Hobbes on heat and cold
Reference: De Corpore 28

Number: 1.22
Topic: Hobbes on sound
Reference: De Corpore 29

Number: 1.23
Topic: Clarification of claims in previous letter; puzzles about transfer of motion; the relation of motions to bodies; occasional as opposed to prime and principal causes

Number: 1.24
Topic: Echoes

Number: 1.25
Topic: Echoes again, and images in mirrors

Number: 1.26
Topic: Light and transparent bodies

Number: 1.27
Topic: Volume in different spaces

Number: 1.28
Topic: Hobbes on scent
Reference: De Corpore 29

Number: 1.29
Topic: Hobbes on density and rarity
Reference: De Corpore 30

Number: 1.30
Topic: Descartes on motion
Reference: Principles 2.25, 2.40, 2.54

Number: 1.31
Topic: Descartes on place
Reference: Principles 2.10-4

Number: 1.32
Topic: Place again

Number: 1.33
Topic: Descartes, vortices, etc
Reference: Principles 3.46

Number: 1.34
Topic: Descartes on rarefaction
Reference: Principles 2.6-7

Number: 1.35
Topic: Descartes on the mind being really distinct from the body
Reference: Principles?

Number: 1.36
Topic: Descartes on animals’ lacking reason
Reference: Discourse 5

Number: 1.37
Topic: Descartes on sense and perception
Reference: Principles 4.189, Dioptrics 1.2-3, 4.1

Number: 1.38
Topic: Descartes on the little parts of things
Reference: Meteor 1.3, 3.1

Number: 1.39
Topic: Descartes on vapour, clouds, wind, rain
Reference: Meteor, ch 2, 4, 5, 6

Number: 1.40
Topic: Descartes on colours and little spheres
Reference: Optics?

Number: 1.41
Topic: Descartes on fire
Reference: Principles 4.97, 4.107

Number: 1.42
Topic: Concluding section on Hobbes and Descartes by restating own basic view

Number: 1.43
Topic: Assorted questions about own view answered

Number: 1.44
Topic: Assorted questions about own view answered

Number: 1.45
Topic: Assorted questions about own view answered

Section 2. More

Number: 2.1
Topic: More on arguing for God’s existence
Reference: Antidote against Atheism 1.10.5

Number: 2.2
Topic: On whether we have an idea of God

Number: 2.3
Topic: More on knowledge of God
Reference: Immortality of the Soul 1.1.4

Number: 2.4
Topic: More on enlarging the understanding
Reference: Antidote against Atheism 2.2.1

Number: 2.5
Topic: More on laws of nature
Reference: Antidote against Atheism 2.2-3

Number: 2.6
Topic: More on mortality
Reference: Antidote against Atheism

Number: 2.7
Topic: More against self-moving matter
Reference: Immortality of the Soul 1.1.12

Number: 2.8
Topic: More on the passivity of matter
Reference: Immortality of the Soul

Number: 2.9
Topic: More on the divisibility of matter
Reference: Immortality of the Soul Preface

Number: 2.10
Topic: More against motion being a principle of nature
Reference: Antidote against Atheism Appendix 11

Number: 2.11
Topic: More on the consequences of motion being natural to matter
Reference: Antidote against Atheism 1.2.1

Number: 2.12
Topic: More on self-motion
Reference: Immortality of the Soul 1.1.7

Number: 2.13
Topic: More on whether matter can sense
Reference: Immortality of the Soul 1.2.2

Number: 2.14
Topic: More on whether matter can sense, again
Reference: Immortality of the Soul,6,7

Number: 2.15
Topic: More on perception and figuring
Reference: Immortality of the Soul 2.6

Number: 2.16
Topic: More on perception, sensation, and motion
Reference: Immortality of the Soul Preface

Number: 2.17
Topic: Sense, reason, and outward objects

Number: 2.18
Topic: More on the role of the brain
Reference: Antidote against Atheism 1.11

Number: 2.19
Topic: More on the seat of the common sense
Reference: Immortality of the Soul 2.4

Number: 2.20
Topic: More on More on the mind
Reference: Antidote against Atheism 1.5

Number: 2.21
Topic: More on the existence of a natural incorporeal substance
Reference: Antidote against Atheism 2.2

Number: 2.22
Topic: More on the soul’s indivisibility

Number: 2.23
Topic: More’s comparison between an immaterial spirit and light
Reference: Antidote against Atheism Appendix 3, Immortality of the Soul 1.1.5

Number: 2.24
Topic: Shadows

Number: 2.25
Topic: More on the soul as architect of the body
Reference: Immortality of the Soul 1.2.10

Number: 2.26
Topic: More on the soul as architect of the body again
Reference: Immortality of the Soul 1.2.10

Number: 2.27
Topic: More on passions and sympathies
Reference: Immortality of the Soul 2.10

Number: 2.28
Topic: More on dimness of sight
Reference: Immortality of the Soul 2.6b.8

Number: 2.29
Topic: The supernatural soul

Number: 2.30
Topic: The immortality of the divine soul

Number: 2.31
Topic: More on free-will and necessity
Reference: Immortality of the Soul 1.1.3, 2.2
Note: That is the declared topic at the start, but most of the section continues the discussion of the supernatural soul from the previous two sections, considering whether there is a sense in which supernatural, immaterial beings can be in nature.

Number: 2.32
Topic: More on witches
Reference: Antidote against Atheism 3

Number: 2.33
Topic: On the preexistence of souls
Reference: “the Book that treats of the Pre-existence of Souls, and the Key that unlocks the Divine Providence”. That would be Glanvill (1662).

Number: 2.34
Topic: On the claim that Cavendish has contradicted an earlier view she held

Section 3. van Helmont

Number: 3.1
Topic: Starting out with van Helmont
Reference: Physic Refined, 4. Cavendish appears to have been reading van Helmont (1662). The chapter and treatise titles below refer to parts of this book, though in occasional cases I have given page numbers.

Number: 3.2
Topic: van Helmont’s strange principles
Reference: PR, chapters called The Fiction of Elementary Complexions and Mixtures, Of the Birth and Original of Forms, Of the Ideas of Diseases, The Seat of Diseases in the Soul is confirmed, The Subject of inhering of Diseases is in the point of life, &c, Of the Gas of the Water, Of the Blas of Meteors, Of the Blas of Man, Of the Causes and beginnings of Natural things, Of the Ideas of Diseases, Of things Conceived, or Conceptions
Reference: Of the Magnetick cure of wounds

Number: 3.3
Topic: van Helmont on elements and diseases
Reference: In his Treatise called. A passive deceiving of the Schools of the Humourists (van Helmont 1662, pp.1015-72)

Number: 3.4
Topic: van Helmont on what freezes water
Reference: Ch. Of the Gas of Water (van Helmont 1662, pp.70-7)

Number: 3.5
Topic: van Helmont’s view that fish are “water transchanged”
Reference: Ch. The Fiction of Elementary Complexions and Mixtures

Number: 3.6
Topic: van Helmont on the moisture of air
Reference: Ch Of Air

Number: 3.7
Topic: van Helmont’s view “That Air is in its nature Cold”

Number: 3.8
Topic: van Helmont on “Wind, Vacuum, Rainbows, Thunder, Lightning, Earth-quakes, and the like”
Reference: Ch. Of the Blas of Meteors, Ch. Of Vacuum, Ch. Of an Irregular Meteor, Ch. Of the Earthquake, Ch. Of the Birth or Original of Forms

Number: 3.9
Topic: On van Helmont on earthquakes again

Number: 3.10
Topic: On van Helmont on “several Seeds of several Creatures”
Reference: several places, including “In the Ch. the Position is demonstrated: and in the ch. called the Authority of the Duumvirate”

Number: 3.11
Topic: On several confusing expression in van Helmont
Reference: Ch. called Magnum oportet, Of the Ideas of Diseases

Number: 3.12
Topic: On van Helmont’s metaphorical talk of nature
Reference: Ch. Nature is ignorant of Contraries, In the Hist. of Tartar., Ch. The Image of the Ferment begets the Mass with Child.

Number: 3.13
Topic: On van Helmont on the art of fire

Number: 3.14
Topic: On van Helmont on sensation
Reference: Of the Disease of the Stone. Ch. 9

Number: 3.15
Topic: On van Helmont on sympathy and antipathy

Number: 3.16
Topic: On van Helmont on witches

Number: 3.17
Topic: On van Helmont on how time relates to motion
Reference: In his Treatise of Time

Number: 3.18
Topic: On van Helmont on the effects of fire on living and dead bodies
Reference: Of the disease of the Stone, Ch. 9.

Number: 3.19
Topic: On van Helmont’s interpretation of scripture
Reference: Ch. The Position is demonstrated.

Number: 3.20
Topic: On van Helmont’s distinction between three kinds of atheists
Reference: Ch. Of the Image of the Mind

Number: 3.21
Topic: On van Helmont’s view that the world is mostly made up os spirits
Reference: Ch. Of the Magnetick cure of wounds

Number: 3.22
Topic: On van Helmont on the soul
Reference: Ch. Of the Image of the Mind, Of the Spirit of life.

Number: 3.23
Topic: On van Helmont’s comparison of the soul and the sun
Reference: Of the seat of the Soul. It. Of the Image of the Mind.

Number: 3.24
Topic: On van Helmont on parts of the soul
Reference: Ch. Of the Image of the Soul.

Number: 3.25
Topic: On van Helmont on reason and intellect
Reference: Ch. The hunting or searching out of Sciences. It. Of the Image of the Mind.

Number: 3.26
Topic: On van Helmont on health and diseases
Reference: Ch. Call’d the Authors answers, Ch. Of the subject of inhering of diseases, Ch. The subject of inhering of diseases is in the point of life, Ch. Of the knowledg of diseases

Number: 3.27
Topic: On van Helmont on health and diseases again
Reference: Ch. Of the knowledg of diseases, Ch. Called the Position

Number: 3.28
Topic: On van Helmont’s comments about physicians
Reference: In his Promises, Column. 3

Number: 3.29
Topic: On van Helmont on the cause of digestion

Number: 3.30
Topic: On van Helmont on digestion again
Reference: Ch. Of a Six-fold digestion, The passive deceiving of the Schools, the humorists, C. I., Ch. Heat doth not digest efficiently

Number: 3.31
Topic: On humors

Number: 3.32
Topic: On the purging of the brain
Reference: Ch. Call’d The Erring Watchman, or Wandring Keeper, Ch. call’d The Spirit of Life

Number: 3.33
Topic: On van Helmont against blood-letting
Reference: In his Treatise of Fevers, c. 4

Number: 3.34
Topic: On van Helmont against purging medicines
Reference: In his Treatise of Fevers, c. 5

Number: 3.35
Topic: On van Helmont’s opposition to “Issues, Cauteries, Clysters, and the like”
Reference: Of Cauteries

Number: 3.36
Topic: On van Helmont’s view “That Drink ought not to be forbidden in Fevers”
Reference: Of Fevers, Ch. 12

Number: 3.37
Topic: On van Helmont on “Chymical Medicines”
Reference: Of Fevers, ch 14; Ch. Of the manner of entrance of things darted into the body

Number: 3.38
Topic: On van Helmont’s opposition to certain treatments
Reference: Of the disease of the Stone, c. 3; Ch. Of the reason or consideration of diet.

Number: 3.39
Topic: On van Helmont on the plagues of beast and men
Reference: In the Plaguegrave, ch. 17

Number: 3.40
Topic: On van Helmont on bladder stones and kidney stones
Reference: Of the Stone, ch 6. See the ch. called, A Numero-Critical Paradox of supplies

Number: 3.41
Topic: On van Helmont on gout
Reference: Of the disease of the Stone. c. 9; Of the Spirit of Life

Number: 3.42
Topic: On van Helmont on “whether some cures of diseases may be effected by bare co-touchings”
Reference: In the ch. call’d Butler

Number: 3.43
Topic: On van Helmont on a sudden death without decay or disorder in the body
Reference: Ch. 61. called, The Preface.

Number: 3.44
Topic: On being weakened by disease

Number: 3.45
Topic: Conclusion of section 3

Section 4. Other philosophers

Number: 4.1
Topic: On generation

Number: 4.2
Topic: On generation, with some reference to Harvey

Number: 4.3
Topic: On generation again

Number: 4.4
Topic: On Galileo on upwards, downwards, forwards, and backwards, and circular and straight

Number: 4.5
Topic: On Galileo on degrees of motion

Number: 4.6
Topic: On transfer of motion

Number: 4.7
Topic: On “Whether Respiration be common to all animal Creatures?”

Number: 4.8
Topic: On place, with reference to “that Learned Author Dr. Ch[arleton]“
Reference: Charleton (1654, ch. 6)

Number: 4.9
Topic: On time, with reference to Ch[arleton] again
Reference: Charleton (1654, ch.7)

Number: 4.10
Topic: On a “new Author that treats of Natural Philosophy” on infinite matter
Reference: Gideon Harvey 1663, the second part, the first book, chapter 8, “Of the Principles of a Natural Being”

Number: 4.11
Topic: On that same author again, on water
Reference: Gideon Harvey 1663, perhaps the second part, the first book, chapter 8, “Of the absolute and Respective Form of Earth, Water, Ayr, and Fire”

Number: 4.12
Topic: On the weight of water

Number: 4.13
Topic: On water again

Number: 4.14
Topic: On water, with reference to “an Author, who is of opinion, That Snow is nothing else but Ice broken or ground into small pieces”
Reference: ?
Note: Who is this author?

Number: 4.15
Topic: On “several questions out of your new Author”
Note: Is this the same author as in the previous note?

Number: 4.16
Topic: On “the ascending nature of fire”

Number: 4.17
Topic: On assorted further questions

Number: 4.18
Topic: On the extent to which Cavendish understands other philosophers

Number: 4.19
Topic: Cavendish’s opinion of the philosophers themselves

Number: 4.20
Topic: On logic and sophistry

Number: 4.21
Topic: On the trinity, with reference to a conversation with “Lady N. M.”
Note: Who is Lady N.M.? Is N.M. just a device to give another voice to Cavendish (M.N.)?

Number: 4.22
Topic: On “that Learned and Ingenious Writer B” and “the Book call’d, The Discourses of the Virtuosi in France”
Reference: Havers (trans.) (1664)
Note: I wonder whether B, with his “experiments”, is Robert Boyle.

Number: 4.23
Topic: On assorted further questions
Reference: Includes a references to a Mr V.Z., and his questions “concerning those glasses, one of which being held close in ones hand, and a little piece being broke of its tail, makes as great a noise as the discharging of a Gun”

Number: 4.24
Topic: On learning nature’s secrets using microscopes and other machines.

Number: 4.25
Topic: On the division of religion.

Number: 4.26
Topic: On predestination, with reference to “Sir P. H. and Sir R. L.”
Note: Who are “Sir P. H. and Sir R. L.”?

Number: 4.27
Topic: On failings of Cavendish’s Philosophical Opinions, and on whether we can know the truth in natural philosophy

Number: 4.28
Topic: On the wisdom of nature

Number: 4.29
Topic: On assorted further questions

Number: 4.30
Topic: On Cavendish’s panpsychism

Number: 4.31
Topic: Clarification of various opinions

Number: 4.32
Topic: On whether matter is eternal

Number: 4.33
Topic: A series of further clarifications


(All seventeenth-century English language works published in London, unless otherwise stated.)

Boyle, Robert. I suggested above that the “B” of 4.22 might be Robert Boyle. He had already published several works by 1664, such as
—. 1660. New experiments physico-mechanicall, touching the spring of the air, and its effects (made, for the most part, in a new pneumatical engine).

Cavendish, Margaret. 1655. Philosophical and Physical Opinions.
—. 1664. Philosophical letters, or, Modest reflections upon some opinions in natural philosophy maintained by several famous and learned authors of this age, expressed by way of letters.

Charleton, Walter. 1654. Physiologia Epicuro-Gassendo-Charltoniana, or, A fabrick of science natural, upon the hypothesis of atoms founded by Epicurus repaired [by] Petrus Gassendus ; augmented [by] Walter Charleton.

Descartes, René. Cavendish refers to several of Descartes’s works. Some of these were available in published English translations. The others she presumably had translated for her.
—. 1649. A discourse of a method for the well-guiding of reason, and the discovery of truth in the sciences. Published English translation.
—. 1650. The Passions of the Soule. Published English translation.
—. Principles of Philosophy.
—. Meteors.
—. Optics.

Du Verger, Suzanne. 1657. Du Vergers humble reflections upon some passages of the Right Honorable the Lady Marchionesse of Newcastles Olio.

Galileo. 4.4 and 4.5 consider “the Works of that most famous Philosopher and Mathematician of our age Gal.”

Glanvill, Joseph. 1662. Joseph Glanvill’s Lux orientalis, or, An enquiry into the opinion of the Eastern sages concerning the praeexistence of souls being a key to unlock the grand mysteries of providence, in relation to mans sin and misery.

Harvey, Gideon. 1663. Archelogia philosophica nova, or, New principles of philosophy containing philosophy in general, metaphysicks or ontology, dynamilogy or a discourse of power, religio philosophi or natural theology, physicks or natural philosophy.

Harvey, William. 4.2 discusses “the Book of that most learned and famous Physician and Anatomist, Dr. Harvey, which treats of Generation”. That would be
—. 1653. Anatomical exercitations concerning the generation of living creatures to which are added particular discourses of births and of conceptions.

Havers, G. (trans.). 1664. A general collection of discourses of the virtuosi of France, upon questions of all sorts of philosophy, and other natural knowledg made in the assembly of the Beaux Esprits at Paris, by the most ingenious persons of that nation / render’d into English by G. Havers, Gent..

Hobbes, Thomas. Cavendish refers to two of Hobbes’ works, Leviathan and the English version of De Corpore.
—. 1651. Leviathan.
—. 1656. Elements of Philosophy, the First Section Concerning Body. English translation of Hobbes’s 1655 De Corpore.

More, Henry. Cavendish refers to two of More’s works, the Immortality of the Soul and the Antidote against Atheism. These were available in more than one edition, as below.
—. 1653. Antidote against Atheism. First edition.
—. 1655. Antidote against Atheism. Second edition.
—. 1659. The Immortality of the Soul.
—. 1662. A collection of several philosophical writings of Dr Henry More … as namely, his Antidote against atheism, Appendix to the said antidote, Enthusiasmus triumphatus, Letters to Des-Cartes, &c., Immortality of the soul, Conjectura cabbalistica.

Narramore, Kathyrn Coad. 2013. “Du Vergers Humble Reflections and Dedicatory Epistles as Public Sphere”. Prose Studies: History, Theory, Criticism 35: 139-53.

Sarasohn, Lisa T. 2010. The Natural Philosophy of Margaret Cavendish. Baltimore: Johns Hopkins University Press.

van Helmont, J.B. 1662. Oriatrike, or, Physick refined. The common errors therein refuted, and the whole art reformed & rectified: being a new rise and progress of phylosophy and medicine for the destruction of diseases and prolongation of life. / Written by that most learned, famous, profound, and acute phylosopher, and chymical physitian, John Baptista Van Helmont … now faithfully rendered into English, in tendency to a common good, and the increase of true science; by J.C. sometime of M.H. Oxon.

Suggested citation:

Duncan, Stewart. “Letters in the Philosophical Letters.” Digital Cavendish Project. 5 November 2014.