Sources and References

Primary texts

• Descartes, René. Meditations on First Philosophy. Trans. John Cottingham. Cambridge: Cambridge University Press, 1996.
• Descartes, René. Discourse on Method and Related Writings. Trans. Desmond Clarke. London: Penguin, 1999.
• Descartes, René. Principles of Philosophy. Trans. Valentine Rodger Miller and Reese P. Miller. Dordrecht: Reidel, 1983.
• Elisabeth of Bohemia and René Descartes. The Correspondence Between Princess Elisabeth of Bohemia and René Descartes. Trans. and ed. Lisa Shapiro. Chicago: University of Chicago Press, 2007.
• Spinoza, Baruch. Ethics. Trans. Edwin Curley. In A Spinoza Reader. Princeton: Princeton University Press, 1994.
• Spinoza, Baruch. Theological-Political Treatise. Trans. Samuel Shirley. Indianapolis: Hackett, 2001.
• Cavendish, Margaret. Observations Upon Experimental Philosophy. Ed. Eileen O’Neill. Cambridge: Cambridge University Press, 2001.
• Cavendish, Margaret. Grounds of Natural Philosophy. London, 1668. Facsimile reprint, West Cornwall: Locust Hill Press, 1996.
• Leibniz, G. W. Monadology and Other Philosophical Essays. Trans. Paul Schrecker and Anne Martin Schrecker. Indianapolis: Bobbs-Merrill, 1965.
• Leibniz, G. W. Discourse on Metaphysics and Other Essays. Trans. Daniel Garber and Roger Ariew. Indianapolis: Hackett, 1991.
• Leibniz, G. W. New Essays on Human Understanding. Trans. and ed. Peter Remnant and Jonathan Bennett. Cambridge: Cambridge University Press, 1996.
• Locke, John. An Essay Concerning Human Understanding. Ed. Peter Nidditch. Oxford: Clarendon Press, 1975.
• Berkeley, George. A Treatise Concerning the Principles of Human Knowledge and Three Dialogues Between Hylas and Philonous. Ed. Howard Robinson. Oxford: Oxford University Press, 1996.
• Hume, David. A Treatise of Human Nature. Ed. L. A. Selby-Bigge and P. H. Nidditch. Oxford: Clarendon Press, 1978.
• Hume, David. An Enquiry Concerning Human Understanding. Ed. Tom Beauchamp. Oxford: Oxford University Press, 1999.
• Reid, Thomas. Inquiry into the Human Mind on the Principles of Common Sense. Ed. Derek Brookes. Edinburgh: Edinburgh University Press, 1997.
• Reid, Thomas. Essays on the Intellectual Powers of Man. Ed. Derek Brookes and Knud Haakonssen. Edinburgh: Edinburgh University Press, 2002.

Secondary texts

• Garber, Daniel. Descartes’ Metaphysical Physics. Chicago: University of Chicago Press, 1992.
• Hatfield, Gary. Descartes and the Meditations. London: Routledge, 2003.
• Della Rocca, Michael. Spinoza. London: Routledge, 2008.
• James, Susan. “Margaret Cavendish’s Philosophy.” In A History of Women Philosophers, vol. 3, ed. Mary Ellen Waithe. Dordrecht: Kluwer, 1991.
• Cunning, David. Cavendish. Cambridge: Cambridge University Press, 2016.
• Rutherford, Donald. Leibniz and the Rational Order of Nature. Cambridge: Cambridge University Press, 1995.
• Ayers, Michael. Locke: Epistemology and Ontology. London: Routledge, 1991.
• Stroud, Barry. Hume. London: Routledge, 1977.
• Cuneo, Terence, and René van Woudenberg, eds. The Cambridge Companion to Thomas Reid. Cambridge: Cambridge University Press, 2004.
• Shapiro, Lisa. “Princess Elisabeth and Descartes: The Union of Soul and Body and the Practice of Philosophy.” British Journal for the History of Philosophy 7, no. 3 (1999): 503–520.

Online resources

• Stanford Encyclopedia of Philosophy (SEP): entries on Descartes, Elisabeth of Bohemia, Spinoza, Cavendish, Leibniz, Locke, Berkeley, Hume, Reid, and related topics. Available at https://plato.stanford.edu.
• Early Modern Texts (Jonathan Bennett, ed.): modernized editions of primary texts. Available at https://www.earlymoderntexts.com.

Chapter 1: The Modern Turn — Descartes and the Meditations

1.1 What Makes Philosophy “Modern”?

The label “early modern philosophy” refers to the roughly two-century period from Descartes (1596–1650) to Kant (1724–1804), during which European philosophers decisively broke from the Aristotelian–Scholastic tradition that had dominated medieval universities. The rupture was not merely stylistic; it was methodological and metaphysical. Where Scholastic philosophers analyzed nature in terms of substantial forms, final causes, and the authority of Aristotle, the early moderns sought certainty grounded in reason alone or in controlled observation of nature.

Three interlocking transformations define the modern turn:

1. Methodological individualism (方法论个人主义): The locus of philosophical authority shifts from tradition and ecclesiastical sanction to the individual rational subject. Descartes begins the Meditations in solitude, resolving to doubt everything he cannot certify for himself.

2. The new science: The Galilean and later Newtonian revolution in natural philosophy required a new metaphysical foundation. Questions about the nature of matter, extension, motion, and causation became urgent in ways they had not been since antiquity.

3. The problem of the external world: Once the mind is made the starting point of philosophical inquiry, the relationship between mental representations and the external world becomes a permanent philosophical problem — one that the rationalists, empiricists, and eventually Kant each address in distinctive ways.

1.2 Descartes: Life and Context

René Descartes was born in La Haye en Touraine in 1596 and educated by Jesuits at La Flèche, where he received a thorough grounding in Scholastic philosophy and mathematics. His dissatisfaction with Scholastic philosophy is recorded in the opening of the Discourse on Method (1637): despite years of study he felt he had learned nothing certain except mathematics. After years of travel and military service, Descartes settled in the Netherlands, where the relative intellectual freedom allowed him to develop and publish his system. The Meditations on First Philosophy appeared in 1641, accompanied by Objections and Replies from Mersenne, Hobbes, Gassendi, and others — an extraordinary philosophical exchange that illuminates Descartes’s project from multiple angles.

1.3 The Method of Doubt

The Meditations opens not with a positive claim but with an act of suspension. Descartes resolves to withhold assent from everything he can doubt, however slightly, in order to find something — if anything — that is truly certain.

Descartes deploys three progressively more radical skeptical hypotheses:

• The Senses Argument: The senses sometimes deceive (mirages, optical illusions). A wise person never fully trusts what has deceived them even once.
• The Dream Argument (梦境论证): Even if the senses are usually reliable, we cannot at any moment rule out that we are dreaming. The coherence of a dream from the inside is indistinguishable from waking experience.
• The Evil Demon Hypothesis (恶魔假设): Descartes imagines a supremely powerful and malicious deceiver who causes him to be wrong even about mathematical truths that seem self-evident — such as that 2 + 3 = 5.

The third hypothesis is crucial because it extends doubt beyond empirical belief to a priori judgments. If the demon hypothesis cannot be refuted, nothing is certain.

1.4 The Cogito

In Meditation II Descartes finds his Archimedean point. Even if an evil demon is deceiving him, the very act of being deceived entails that he exists as a thinking thing:

The cogito (我思故我在) is typically analyzed as a performance rather than a syllogism: in the very act of doubting, thinking, or entertaining any thought whatsoever, the existence of a thinking subject is immediately and undeniably revealed. No inference from a general premise (“whatever thinks, exists”) is needed; the indubitability is direct.

What is the self that the cogito reveals? Descartes’s answer is striking: a res cogitans (思维实体) — a thinking thing, whose essence is thought alone. The body, as something extended and in principle capable of being doubted, is not part of the essential self disclosed by the cogito. This sets up the mind–body dualism that will haunt the rest of early modern philosophy.

1.4.1 The Criterion of Clear and Distinct Perception

From the cogito Descartes extracts a general epistemic principle: whatever he perceives clearly and distinctly (清晰且明确地) is true. The cogito is the model of such a perception — it is perfectly transparent to reason. This criterion governs the rest of the Meditations: all subsequent claims to knowledge must meet this standard.

Chapter 2: Descartes — God, Mind, and Body

2.1 The Existence of God: Two Arguments

Descartes requires God’s existence for two interconnected reasons: (a) to validate the criterion of clear and distinct perception, and (b) to guarantee that the external world exists and corresponds to our clear and distinct ideas of it. He offers two main arguments.

2.1.1 The Causal Argument (Meditation III)

Descartes reasons from the existence of his idea of a supremely perfect, infinite being. Since an idea must have a cause at least as real as the representational content of the idea (the principle of adequate causation, 充足因原则), and since he, a finite and imperfect being, cannot be the cause of an idea with infinite objective reality, the idea of God must have been caused by God himself. This is a cosmological argument applied to the content of ideas rather than to things in the world.

2.1.2 The Ontological Argument (Meditation V)

Existence belongs to God’s essence as necessarily as three angles belong to a triangle. God is defined as a supremely perfect being; necessary existence is a perfection; therefore God necessarily exists. This is a version of the ontological argument (本体论论证) first formulated by Anselm of Canterbury, here reworked in terms of Descartes’s conceptual framework.

2.2 The Cartesian Circle

The Cartesian circle (笛卡尔循环) is the most famous objection to Descartes’s epistemological project, raised in the Fourth Objections by Antoine Arnauld:

• Descartes uses clear and distinct perception to prove that God exists.
• He then uses the existence of God (a non-deceiving God) to certify that clear and distinct perception is reliable.

If the reliability of clear and distinct perception depends on God’s existence, and God’s existence depends on clear and distinct perception, the argument is circular.

Descartes’s response distinguishes between currently attended clear and distinct perceptions (whose truth is self-guaranteeing in the moment) and remembered or general beliefs. God is needed to guarantee the reliability of the latter — to assure Descartes that what seemed clearly and distinctly true yesterday is still true today even when he is not attending to it.

2.3 Real Distinction: Mind and Body

With God’s existence established, Descartes proceeds in Meditation VI to prove that mind and body are really distinct (实在区分) substances. The argument runs: he can clearly and distinctly conceive of mind without body and body without mind; God can bring about whatever is clearly and distinctly conceivable as separate; therefore mind and body are really distinct.

2.3.1 The Problem of Interaction

If mind and body share no properties, how do they causally interact? Descartes acknowledges in Meditation VI and in his correspondence that mind and body do interact — the will moves the arm, and the pinprick causes pain. He locates the site of interaction in the pineal gland (松果体) in the brain, a unique, unpaired structure he thought could be moved by the “animal spirits” that mediate sensation and motion. This anatomical hypothesis satisfied almost no one; as Elisabeth of Bohemia pointed out with devastating precision, identifying a physical site does not explain how a non-extended substance can push anything.

2.4 The Material World and Primary/Secondary Qualities

Descartes argues that the material world exists and that its fundamental properties are those that correspond to our clear and distinct ideas: extension (广延), figure, motion, and number. Properties like color, heat, and sound as experienced — what Locke would later call secondary qualities (次生性质) — are not in bodies as we perceive them; they are effects of primary properties on our sensory apparatus.

Chapter 3: Elisabeth of Bohemia and the Mind–Body Problem

3.1 Elisabeth in Philosophical Context

Princess Elisabeth of Bohemia (1618–1680) is not a peripheral figure who merely prompted Descartes to clarify his views. She is a rigorous philosophical interlocutor who identified what remains to this day the central problem with Cartesian dualism. Her correspondence with Descartes, conducted from 1643 until his death in 1650, constitutes some of the most philosophically acute material of the entire period. Lisa Shapiro’s 2007 translation and edition, based on the complete correspondence, has renewed scholarly attention to Elisabeth’s contribution.

3.2 The Central Objection: How Can an Unextended Substance Move a Body?

In her first letter to Descartes (May 6, 1643), Elisabeth poses the question with surgical precision:

This is not a request for clarification; it is a logical challenge. Causal interaction in the mechanistic framework requires contact, and contact requires extension. Since Elisabeth accepts Descartes’s physics but not his account of mental causation, she demands a positive explanation — not a relocation of the mystery to the pineal gland.

3.2.1 Descartes’s Response and Its Inadequacy

Descartes’s responses are notable for their evasiveness. He suggests that the union of mind and body is a primitive notion (原始概念) — one of three fundamental notions (along with mind alone and body alone) that cannot be explained in terms of anything simpler. He further suggests that the sensation of heaviness (gravity) shows that we can conceive of a non-extended thing moving a body, since the Scholastics understood gravity as an immaterial quality that nonetheless moved matter downward.

Elisabeth rejects this analogy immediately: the Scholastics were wrong about gravity, and in any case Descartes himself had rejected Scholastic qualities. An analogy to a discredited view is no explanation at all.

3.3 Elisabeth on the Passions and the Good Life

The correspondence extends beyond metaphysics. Elisabeth raises questions about the passions — the emotions and feelings that arise from the mind-body union — and about how a person can achieve well-being in conditions of suffering. She herself suffered from persistent illness and the political catastrophe of her family’s exile from the Palatinate.

These exchanges prompted Descartes to write The Passions of the Soul (1649), dedicated to Elisabeth. Here Elisabeth’s practical philosophical concerns — how to manage fear, grief, and despair in a life of genuine adversity — drive Descartes’s most sustained engagement with moral philosophy. Elisabeth’s questions show that the mind-body problem is not merely a metaphysical puzzle but has direct implications for ethics and the philosophy of action.

3.4 Philosophical Significance of Elisabeth’s Contribution

Elisabeth’s letters accomplish three things that standard textbook treatments of Descartes omit:

1. They show that the mind-body problem is immediately apparent to a contemporary reader who accepts Descartes’s premises — it is not a later problem imposed on Descartes by critics.
2. They force a distinction between what is philosophically explicable and what must be accepted as a primitive, lived unity — a distinction that anticipates phenomenological approaches in the 20th century.
3. They expand the scope of early modern philosophy to encompass practical reason, the passions, and the conditions of a good life under adversity.

Chapter 4: Spinoza — Substance Monism, God, and Human Freedom

4.1 Spinoza’s Life and the Radical Enlightenment

Baruch de Spinoza (1632–1677) was excommunicated from the Amsterdam Jewish community in 1656 at the age of 23 — the most severe such censure recorded in the community’s history. The grounds are unknown, but his philosophical views, which denied the personality of God, the special status of the Hebrew people, and the immortality of the individual soul, would have been more than sufficient. He lived simply as a lens-grinder, declining academic positions and royal patronage in order to preserve his intellectual independence. The Ethics, his masterwork, was completed by 1675 but published posthumously in 1677.

4.2 The Geometric Method

Spinoza presents the Ethics in geometric form: definitions, axioms, propositions, demonstrations, and corollaries, modeled on Euclid’s Elements. This is not mere stylistic peculiarity. Spinoza believed that philosophical truths, like mathematical truths, are necessary — they could not be otherwise. The geometric form enacts this conviction: if the definitions and axioms are correct and the demonstrations valid, the conclusions are inescapable.

4.3 Substance, Attributes, and Modes

The fundamental ontological categories of the Ethics are substance (实体), attribute (属性), and mode (样态).

From these definitions and a series of propositions, Spinoza argues that there can be only one substance, that it must be infinite, and that it must be self-caused (causa sui, 自因). This substance is what Spinoza calls God or Nature (上帝即自然, Deus sive Natura) — the single infinite substance with infinitely many attributes, of which we know only two: Thought (思想) and Extension (广延).

4.3.1 Why Only One Substance?

Spinoza’s argument for substance monism (实体一元论) proceeds as follows: if there were two substances, they would have to be distinguished either by their attributes or by their modes. But substances are conceived through themselves; no substance can depend for its nature on what another substance is or is not. Therefore two substances cannot share an attribute; and if they have different attributes, they cannot limit or affect each other — they are, in the relevant sense, the same kind of infinite self-sufficient thing. The pressure of the argument is that genuine independence entails uniqueness at the level of substance.

4.4 God or Nature: Immanence and Pantheism

For Spinoza, God is not a transcendent creator who exists apart from the world and gives it being by an act of will. God is the immanent cause of all things — everything that exists is either God (as substance) or a mode of God. This is a form of pantheism (泛神论), though Spinoza scholars debate whether “pantheism” is precise enough.

The implications are radical:

• There is no creation ex nihilo. The modes of God (particular things, events, thoughts) follow from God’s nature with the same necessity as theorems follow from axioms.
• God has no free will in the ordinary sense. God does not deliberate and choose; the world necessarily unfolds from God’s nature.
• God is not a moral lawgiver. Good and evil, as popularly understood, are not features of reality but projections of human desire and aversion.

4.5 Parallelism and the Mind–Body Problem

Spinoza’s solution to the Cartesian mind-body problem is distinctive. Since there is only one substance, mind and body are not two separate things but two ways of describing the same underlying reality under different attributes (Thought and Extension). Every mental event (an idea) and its corresponding physical event (a body state) are one and the same mode of God described under different attributes. This is the doctrine of psychophysical parallelism (心身平行论).

This avoids the interaction problem entirely: there is no cross-attribute causation because there are no two things to be causally linked. The cost is explaining why the parallel seems so tight — but for Spinoza this is simply what follows from the unity of substance.

4.6 Human Freedom and the Conatus

Individual human beings are finite modes of God. Each finite mode strives to persist in its own being — this striving is the conatus (努力自保) (Ep. IIIP6). Emotions arise from changes in our power of acting: joy (喜悦) is an increase in power, sadness (悲哀) a decrease.

Freedom (自由) for Spinoza is not freedom from determination (nothing is undetermined) but freedom from external determination. We are free to the extent that our actions flow from our own nature rather than from external forces. Since reason is the highest expression of our nature, a rational life is the freest life. The Ethics Part V argues that understanding sub specie aeternitatis — seeing things under the aspect of eternity — is itself a kind of intellectual joy that constitutes human blessedness.

Chapter 5: Margaret Cavendish — Organic Materialism and Vitalism

5.1 Recovering Cavendish

Margaret Cavendish, Duchess of Newcastle (1623–1673), was one of the most prolific and original philosophers of the seventeenth century, and also one of the most neglected by subsequent historians of philosophy. She published prolifically across genres — natural philosophy, poetry, drama, fiction, and autobiography — at a time when women’s philosophical writing was rarely taken seriously. She was the first woman permitted to attend a meeting of the Royal Society of London (in 1667), though this was a singular concession and not an invitation to membership.

Recent scholarship, especially Eileen O’Neill’s work on Cavendish and David Cunning’s 2016 monograph, has firmly established her as a serious philosophical interlocutor not merely of Descartes but of Hobbes, Gassendi, and the experimentalists of the Royal Society. PHIL 384 treats her in precisely this way.

5.2 Against Mechanism: The Royal Society and Its Critics

The dominant natural philosophy of Cavendish’s time was mechanism (机械论) — the view that all natural phenomena can be explained in terms of the motion and collision of inert particles of matter. Hobbes, Descartes, Boyle, and the experimentalists of the Royal Society all worked within broadly mechanist assumptions, though they disagreed sharply about details.

Cavendish’s Observations Upon Experimental Philosophy (1666) and Grounds of Natural Philosophy (1668) mount a sustained critique of both the philosophical foundations and the practical methodology of mechanism.

5.3 Organic Materialism: Matter Is Alive and Self-Moving

Cavendish’s own position is a form of organic materialism (有机唯物论). She denies the existence of immaterial substances — there is no Cartesian res cogitans — but she also denies the mechanist picture of matter as inert and dead. For Cavendish, all matter is intrinsically alive and self-moving.

5.3.1 Degrees and Kinds of Matter

Cavendish distinguishes three intermixed types or degrees of matter:

These three types are not separately existing things but aspects of one matter that interpenetrate everywhere. Even a stone has rational and sensitive matter intermixed with inanimate matter, though in different proportions than an animal or a human being.

5.3.2 Self-Motion and the Rejection of Mechanism

The mechanist holds that matter is moved only by external impact. Cavendish finds this picture deeply problematic: if matter is inert, then the original impulse for motion must come from outside matter — ultimately from God, as in Descartes’s physics. This makes natural philosophy dependent on theology in a way Cavendish finds philosophically unsatisfying.

If instead matter is intrinsically self-moving, natural phenomena can be explained without invoking a first mover or an immaterial soul. This is Cavendish’s primary motivation for vitalist materialism (活力唯物论): it gives nature a genuine autonomy and explanatory self-sufficiency.

5.4 Perception as Imitation, Not Mechanism

Cavendish’s account of perception is perhaps her most distinctive contribution. Mechanists explain perception by efficient causation: external objects produce motions in the sense organs, which are transmitted through nerves to the brain, where they cause ideas or perceptions.

Cavendish rejects this picture. The problem is what she calls the transmission problem: how does the motion of external particles get “into” the mind? For a dualist like Descartes, the problem of cross-substance causation is acute (as Elisabeth showed). But even for a thoroughgoing mechanist like Hobbes, the question of how brain motion becomes experience is not obviously answered.

Cavendish’s alternative is that perception is a form of imitation (模仿). The sensitive matter of the sense organs “figures out” or imitates the patterns of external objects by producing in itself a representation that resembles the object — not by receiving the object’s motions but by an internal act of patterning. This is a form of active perception (主动感知): the perceiving being is not passively impressed but actively reconstructs.

5.5 Cavendish and Feminist Philosophy of Science

Cavendish’s critique of experimental philosophy has a dimension that is easy to overlook: she is attentive to the gendered sociology of knowledge in ways that anticipate later feminist philosophy of science. The Royal Society was an exclusively male institution. Its experimental practices involved particular social arrangements — who could observe, who could report, whose testimony counted. Cavendish’s outsider status gave her a critical vantage point on these arrangements.

Her visit to the Royal Society in 1667, where Boyle and others performed experiments for her inspection, was ambivalent. She was permitted to see but not to participate. Her subsequent writing continues to insist that natural philosophy requires wisdom and judgment — capacities she clearly possessed — rather than merely instrumental skill with apparatus.

Chapter 6: Leibniz — Monads, Pre-Established Harmony, and Sufficient Reason

6.1 Leibniz’s Polymathic Context

Gottfried Wilhelm Leibniz (1646–1716) is perhaps the most intellectually wide-ranging figure in the history of philosophy. He co-invented the calculus (independently of Newton), developed symbolic logic, made contributions to physics, geology, linguistics, and jurisprudence, and maintained an enormous correspondence with virtually every major intellectual figure of his time. His philosophy was never presented in a single systematic treatise; it must be reconstructed from the Monadology (1714), the Discourse on Metaphysics (1686), the New Essays on Human Understanding (written c. 1704, responding to Locke), and his extensive correspondence.

6.2 Against Cartesian Extension

Leibniz’s metaphysics begins in dissatisfaction with Descartes’s account of matter as pure extension. Extension, Leibniz argues, cannot be the fundamental property of material substance because extension is itself a relational, divisible, and therefore derivative property. Anything extended is in principle divisible; but a substance whose nature is exhausted by divisibility has no genuine unity — it is an aggregate, not a substance.

6.3 Pre-Established Harmony

If monads are windowless — if they do not causally interact — how do mind and body appear to be correlated? How does my intention to raise my arm correspond to my arm rising?

Leibniz’s answer is pre-established harmony (预定和谐). God, at the moment of creation, designed each monad so that its internal sequence of states would unfold in perfect harmony with the states of every other monad — without any subsequent causal interaction between them. The correlation between mind and body is not causal but a divinely engineered coincidence built into the initial conditions of creation.

6.4 The Principle of Sufficient Reason

The Principle of Sufficient Reason (充足理由原则) holds that for everything that is the case, there is a sufficient reason why it is so and not otherwise. Nothing happens without a reason. This principle, together with the Principle of Non-Contradiction (矛盾律), governs all of Leibniz’s metaphysics.

One dramatic application: why does this world exist rather than some other possible world? Leibniz answers that God, being perfectly rational and good, must have a sufficient reason for creating, and that reason is the creation of the best of all possible worlds (可能世界中最好的世界). God surveyed all possible worlds and selected the one with the greatest compossible perfection. This doctrine, memorably satirized by Voltaire in Candide, is Leibniz’s theodicy (神正论) — his justification of God’s goodness in the face of evil.

6.5 Leibniz vs. Locke: Innate Ideas and the Tabula Rasa

The New Essays on Human Understanding is structured as a dialogue between Theophilus (representing Leibniz) and Philalethes (summarizing Locke’s positions). The central dispute concerns innate ideas (先天观念). Locke held that the mind at birth is a blank slate (tabula rasa, 白板). Leibniz responds with the image of a veined block of marble: the veins predispose the marble to be carved into certain shapes rather than others. The mind is not simply passive; it has innate structures that shape experience.

Chapter 7: Locke — Empiricism, Ideas, and the Limits of Knowledge

7.1 The Empiricist Program

John Locke (1632–1704) opens An Essay Concerning Human Understanding (1689) by stating his purpose: to “inquire into the original, certainty, and extent of human knowledge.” His method is explicitly empiricist — he will trace all knowledge back to experience, and in doing so will map the boundaries of what the human mind can legitimately claim to know. This negative or “underlabourer” aspect of the project — clearing the ground of confused claims — is as important as any positive doctrine.

7.2 The Origin of Ideas: Against Innate Ideas

Book I of the Essay is an extended polemic against innate ideas. Locke’s target is the rationalist claim (associated with Descartes and later Leibniz) that certain ideas or principles are present in the mind from birth, prior to and independent of experience.

Locke’s strategy is empirical: if innate ideas existed, we should find universal consent to them among all human beings. But we do not — children, idiots, and “savages” (Locke’s term, reflecting the colonialist assumptions of his time) do not assent to allegedly innate logical principles. Locke concludes that no ideas are innate.

7.3 Simple and Complex Ideas

Book II develops Locke’s positive account of the origin and nature of ideas. All ideas come from two sources:

• Sensation (感觉): experience of external objects through the five senses.
• Reflection (反思): the mind’s observation of its own operations — perceiving, thinking, doubting, willing.

Simple ideas (简单观念) are the atomic elements of thought: a single, uniform appearance or perception that the mind cannot break down further (the idea of red, the idea of cold, the idea of pleasure). Simple ideas are entirely passive — the mind receives them from experience and cannot create them.

Complex ideas (复杂观念) are the mind’s own constructions: combinations, comparisons, and abstractions built from simple ideas. Ideas of substances (gold, man), modes (triangle, gratitude), and relations (cause and effect, identity) are all complex.

7.3.1 Primary and Secondary Qualities

Locke draws a crucial distinction between primary qualities (初级性质) and secondary qualities (次级性质):

This distinction carries a strong realist commitment: there really are properties in the external world (primary qualities) that our ideas accurately represent, while secondary qualities are mind-dependent effects of primary quality configurations on our sensory apparatus.

7.4 The Limits of Human Knowledge

Book IV of the Essay addresses knowledge itself — defined by Locke as “the perception of the connexion and agreement, or disagreement and repugnancy, of any of our ideas” (IV.i.2). On this view, knowledge is always about relations among ideas, never a direct grasp of things in themselves.

This leads to Locke’s skeptical conclusion: we cannot have real knowledge (实在知识) of the inner constitutions of substances. We do not perceive the real essences — the underlying microstructural properties — of gold, water, or the human body. We know only their nominal essences (名义本质): the cluster of observable properties by which we classify things under names. Real essences are, in principle, beyond our epistemic reach.

7.5 Personal Identity

Locke’s account of personal identity (人格同一性) in Book II, Chapter 27 is one of his most original contributions. Personal identity is constituted not by the continuity of a soul or a body but by memory (记忆) and consciousness (意识). A person at time t₂ is the same person as a person at time t₁ if and only if the person at t₂ can remember, from the inside, the experiences of the person at t₁.

This account has sweeping moral and legal implications: moral and legal responsibility should track psychological continuity, not biological continuity. Locke’s account launched a debate that runs through Butler, Hume, Reid, and directly to contemporary personal identity theory.

Chapter 8: Berkeley — Idealism and the Rejection of Matter

8.1 Berkeley’s Puzzle

George Berkeley (1685–1753) accepted almost all of Locke’s epistemological premises and drew from them a conclusion Locke never intended: that matter does not exist. More precisely, Berkeley denied that there are any material substances (物质实体) — unthinking, mind-independent things underlying our perceptions. There are only minds (精神) and the ideas (观念) in minds.

Berkeley’s immaterialism (非物质主义) or subjective idealism (主观唯心论) is captured in his famous formula: esse est percipi (存在即被感知) — “to be is to be perceived.” For ordinary objects like tables and chairs, existence just is being perceived by some mind.

8.2 The Argument from Perception

Berkeley’s primary argument begins with Locke’s own epistemology. We only ever directly perceive our own ideas. The purported material world behind our ideas — the Lockean substratum — is never itself perceived. Locke acknowledged this but thought it reasonable to infer the existence of material substances as the cause and support of our ideas. Berkeley argues that this inference is incoherent.

8.2.1 Against the Primary/Secondary Quality Distinction

Berkeley targets Locke’s distinction between primary and secondary qualities. Locke held that secondary qualities (colors, sounds) are mind-dependent, while primary qualities (extension, figure) are not. Berkeley argues that primary qualities are equally mind-dependent. Extension cannot be perceived apart from color; figure cannot be perceived apart from extension; motion cannot be perceived apart from figure. Since all perception is idea-perception, and since primary qualities cannot be separated from secondary qualities in perception, primary qualities are also mind-dependent.

8.3 God as Guarantor of the Public World

A natural objection: if tables and chairs exist only when perceived, do they wink in and out of existence when no one is looking? Berkeley’s answer involves God. God is an infinite mind who perceives all things at all times; the ideas God perceives constitute the stable, law-governed world of nature. The regularity of nature — what we call natural laws — is the pattern in God’s perception, communicated to us as the language of nature.

8.4 Three Dialogues: Philonous and Hylas

The Three Dialogues Between Hylas and Philonous (1713) presents Berkeley’s arguments in dialogue form, with Philonous (“lover of mind”) representing Berkeley and Hylas (“matter”) representing the materialist. The dialogue format allows Berkeley to present objections sympathetically and answer them in sequence. It remains one of the most pedagogically effective presentations of an early modern philosophical position.

Chapter 9: Hume — Skepticism, Causation, and Personal Identity

9.1 Hume’s Radical Empiricism

David Hume (1711–1776) pushed empiricist principles further than any predecessor, arriving at conclusions so skeptical that he described his own philosophy as a “mitigated skepticism” — a skepticism about the foundations of our beliefs that is nevertheless compatible with ordinary practice and inquiry. His two major philosophical works are A Treatise of Human Nature (1739–40) and An Enquiry Concerning Human Understanding (1748), the latter a more polished reworking of parts of the Treatise.

9.2 Impressions and Ideas

Hume’s empiricism begins with a strict division of all mental contents into impressions (印象) and ideas (观念). Impressions are vivid, forceful — sensory experience and immediate emotional feeling. Ideas are fainter copies of impressions: thoughts, images, memories. The key principle is the copy principle (摹写原则): every simple idea is a copy of a corresponding simple impression.

9.2.1 The Missing Shade of Blue

Hume himself notes a counterexample: if someone has seen every shade of blue except one, they can imagine the missing shade even without the corresponding impression. Hume acknowledges this as an exception but does not revise the copy principle — suggesting that the principle is a heuristic rather than an exceptionless law.

9.3 Causation: The Central Problem

Hume’s analysis of causation (因果关系) is the most influential part of his philosophy. We believe that causes necessitate their effects — that when one billiard ball strikes another, the first makes the second move. Hume asks: what is the impression from which the idea of necessary connection (必然联系) is derived?

His answer is that no impression of necessary connection is ever observed between events. We observe constant conjunction — event A is always followed by event B — but we never observe the connection itself. We infer it.

This is Hume’s famous skeptical solution (怀疑论解决方案): the idea of necessary connection is real, but its source is psychological habit (custom, 习惯), not rational insight into the nature of things. We cannot justify our causal inferences by reason; they are grounded in nature — in the way the mind works.

9.3.1 The Problem of Induction

Hume’s analysis of causation entails a general problem for inductive inference. We infer from past regularities to future regularities. What justifies this inference? Not reason — for it is not a contradiction to suppose the future will differ from the past. Not experience — for to justify induction by appeal to its past success would be circular. Hume concludes that induction (归纳) cannot be rationally justified; it is grounded in natural instinct and custom.

This is the problem of induction (归纳问题), one of the most discussed problems in epistemology and philosophy of science. Kant famously claimed that Hume’s problem “woke him from his dogmatic slumber.”

9.4 Personal Identity: The Bundle Theory

Hume turns the copy principle on the self. Locke grounded personal identity in memory-consciousness. Hume asks: is there an impression of a continuous, identical self? He reports that when he enters most intimately into himself, he always stumbles on some particular perception — a heat or cold, light or shade, love or hatred — but never the self itself.

The conclusion is Hume’s bundle theory (捆束理论) of personal identity: the self is not a substance or a single ongoing entity but a bundle of perceptions (知觉的捆束) — a rapidly changing stream of impressions and ideas held together by relations of resemblance, causation, and especially memory. There is no owner of perceptions; there are only the perceptions.

9.5 Hume on Miracles and Natural Religion

In Section X of the Enquiry, Hume argues that we are never rationally justified in believing miracle reports. The evidence for the regular course of nature is always stronger than the evidence (human testimony) for an exception to it. This is not a proof that miracles do not occur; it is a claim about what a rational person, assessing testimony against background evidence, should believe.

The Dialogues Concerning Natural Religion (published posthumously, 1779) presents Hume’s critique of the design argument, the cosmological argument, and the problem of evil, in a form that remains one of the most searching philosophical treatments of natural theology.

Chapter 10: Reid — Common Sense Realism

10.1 Reid’s Philosophical Context

Thomas Reid (1710–1796) was professor of moral philosophy at Glasgow and the founder of what came to be called the Scottish Common Sense Philosophy (苏格兰常识哲学). Reid’s philosophy is best understood as a systematic response to Hume — a response that accepts many of Hume’s premises about the limits of empiricist reason but rejects what Reid sees as the absurd conclusions those premises yield.

10.2 The Theory of Ideas and Its Discontents

Reid identifies the root of Humean skepticism in a shared assumption he calls the theory of ideas (观念论): the view, common to Descartes, Locke, Berkeley, and Hume, that the immediate objects of perception are not external things but mental entities — ideas, impressions, or representations. If all we ever directly perceive are our own ideas, then the external world is at best inferred, and the self is at best a bundle of impressions. Reid argues that this starting point is the source of all the problems.

10.3 Direct Realism and Common Sense Principles

Reid proposes direct realism (直接实在论) as an alternative. We do not perceive ideas of tables; we perceive tables. Perception puts us in direct epistemic contact with the external world. The intervening ideas are a philosophical fiction.

But how does Reid respond to the skeptical pressure that motivated the theory of ideas in the first place? His answer appeals to first principles of common sense (常识第一原则) — propositions that are so fundamental to all thought and action that their denial is practically incoherent even if they cannot be deductively proved.

10.3.1 The First Principles as Non-Inferential Entitlements

Reid distinguishes between beliefs that require justification (ordinary empirical beliefs, which must be supported by evidence or inference) and first principles, which function as the bedrock of rational inquiry. To demand proof of a first principle is to misunderstand its epistemic status. As Reid argues: if I demand a reason to believe I am not dreaming, I have already conceded that the demand makes sense — but no empirical argument can settle it (Hume showed this). The appropriate response is to recognize that the demand for proof beyond common sense is itself philosophically confused.

10.4 Perception, Sensation, and Conception

Reid introduces a refined analysis of perception that distinguishes it carefully from sensation:

• Sensation (感觉) is a subjective mental state — pain, warmth, color-experience — that has no intentional directedness beyond itself.
• Perception (知觉) involves a conception (概念) of an external object and an immediate, non-inferential belief (信念) in that object’s existence.

When I burn my hand and feel pain, the pain is a sensation — it has no object beyond itself. But when I see a round table, I have a perception of the table: I conceive of it and immediately believe it is there. The belief is not inferred from the sensation; it is immediate.

10.5 Memory and Personal Identity: Against Hume

Reid offers a classic objection to Locke’s memory theory of personal identity. The brave officer paradox: a young boy is flogged for stealing an orchard. He grows up to be a young officer who remembers the flogging. He grows older and becomes a celebrated general who remembers the officer’s battles but has entirely forgotten the flogging. By Locke’s account: the general is the same person as the officer (who remembers the officer’s exploits); the officer is the same person as the boy (who remembers the flogging); but the general is not the same person as the boy (who has no memory of the flogging). This violates the transitivity of identity.

Reid’s own account appeals to the self as a genuine, continuous substance — not a Humean bundle — whose identity over time is basic and unanalyzable. We know ourselves as persistent selves through a primitive form of self-consciousness, not through memory-chains.

10.6 Reid’s Legacy

Reid’s common sense philosophy was enormously influential in the 19th century, especially in Scotland, France (via Cousin), and America. In the 20th century, G. E. Moore’s defense of common sense, and more recently, the epistemological work of William Alston, Alvin Plantinga, and the Reformed epistemologists, all bear the mark of Reidian themes. Reid may be the most philosophically important figure in this course who remains least known to general readers.

Conclusion: The Rationalist-Empiricist Axis and Its Legacy

The standard narrative of early modern philosophy organizes the figures in this course along a rationalist-empiricist axis: Descartes, Spinoza, and Leibniz on one side; Locke, Berkeley, and Hume on the other — with Kant synthesizing both traditions in the critical philosophy. This narrative captures something real: there are genuine disagreements about the role of reason versus experience, innate ideas versus the blank slate, and the possibility of a priori knowledge.

But PHIL 384 has complicated this narrative:

• Elisabeth of Bohemia shows that the mind-body problem is internal to Cartesian rationalism, not an external empiricist critique; and she extends philosophy into the domain of the passions and embodied life.
• Margaret Cavendish undermines the mechanist presuppositions shared by both rationalists and empiricists, proposing instead a vitalist materialism that resists assimilation to either camp.
• Thomas Reid is neither a rationalist nor an empiricist in the standard sense — he accepts direct realism about perception while rejecting both the theory of ideas and the rationalist appeal to innate clear and distinct perceptions.

What unifies the period, perhaps more than any single positive doctrine, is a shared set of problems: the relationship between the mind and the world it seeks to know; the metaphysical structure of substance, causation, and identity; the proper method of inquiry; and the relationship between natural philosophy (science) and philosophy. These problems are not resolved in the period — they are handed to Kant, and through Kant to us.