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5 Leibniz on Mind, Knowledge, and Ideas. Bibliographical Resources (reminder): Descartes’ Meditations free at: http://www.earlymoderntexts.com/f_descarte.html Leibniz’s Nouveau Essays free at: http://www.earlymoderntexts.com/f_leibniz.html. On/by Chomsky :

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Bibliographical Resources (reminder):
  • Descartes’ Meditations free at:


  • Leibniz’s Nouveau Essays free at:


On/by Chomsky:

Chomsky N. (2000). New Horizons in the Study of Language and Mind. Cambridge UP: Cambridge

McGilvray J. (1999). Chomsky: Language, Mind, and Politics. Polity Press: Cambridge

critique of locke
Critique of Locke
  • The New Essays on Human Understanding is an explicit critique of Locke who fails to recognize that the principle of necessary truths are latent in our mind.
  • Locke: matter may think.
  • The main purpose of the Essays is to vindicate the immateriality of the human soul/mind.
Leibniz’s anti-materialism

Materialism is the view that everything that exists is material, or physical.

In short, mental states and processes are either identical to, or realized by, physical states and processes.

The realms of the mental and the physical, for Leibniz, form two distinct realms.

This, though, doesn’t entail, for Leibniz, dualism. That is, the existence of both thinking substance and extended substance (vs. Descartes).

  • Leibniz opposes both materialism and dualism.

He proposes a new view about the relationship between thought and matter.

If the human mind were identical to the brain it would be difficult, if not impossible, to maintain that it is a mirror of God (remember: monades are mirrors of God).
  • The immateriality of the soul/mind also offers a good foundation for the Christian doctrine of the immateriality of the soul and thus of personal immortality. The body decomposes, while the soul survives.
  • We should remember that back in Descartes’ and Leibniz’s time science wasn’t secular.
Most of Leibniz's arguments against materialism are directly aimed at the thesis that perception and consciousness can be given mechanical (i.e. physical) explanation.

Leibniz’s viewpoint is that perception and consciousness cannot possibly be explained mechanically (remember that the science of the time was mechanism).

Therefore, perception and consciousness cannot be physical processes.

Perception and what depends upon it is inexplicable on mechanical principles, that is, by figures and motions.

(In a clock we find parts pushing one another, we don’t find perception, conscious states, thoughts, …)

  • Therefore it is in the simple substance (monade), and not in the composite or in the machine, that one must look for perception.
the mill argument
The Mill Argument
  • Goal: to prove the immateriality of the soul.

Everyone must admit that perception, and everything that depend on it, is inexplicable by mechanical principles, by shape and motion, that is, imagine there were a machine which by its structure produced thought, feelings, and perception. We can imagine it as being enlarged while maintaining the same relative proportions … When we went in we would find nothing but pieces which push one against the other, and never anything to account for perception. Therefore we must look for it in the simple substance and not in the composite, or in a machine. (Monadology WF 270)

The mill argument can be dismiss on the ground that it overlooks the fact that we may lack the understanding or knowledge to see consciousness present in the machine. We’re incapable of coming out with: “Look, a thought over there”. Yet, there may be a thought …
  • The argument is best understood in focusing on the notion of explanation, i.e. there is something about mental life that mechanism cannot explain.
the limits of a mechanistic explanation
The limits of a mechanistic explanation
  • The unity of consciousness cannot be explained invoking mechanistic principles (our mental life is not compartmentalized).

E.g.: clockwork machinery could never explain time-keeping. Water molecules could never explain liquidity.

There are different levels of explanation which may not reduce one to the other.

Leibniz is not offering an argument from ignorance.

He’s not making the fallacious inference:

since we can find no explanation in the machine,

then no explanation could be given.

The machinery could never, in principle, explain the unity of consciousness.

This is a basic premise of the argument against materialism.

  • The direct experience of ourselves is the only direct experience we have of substantial unity.

By means of the soul there is a true unity which corresponds to what is called the I in us; This Icould not occur in artificial machines, nor in the simple mass of matter, however organized it may be.

The human mind being a simple and immaterial substance is also naturally immortal.

The immortality of the mind follows from its simplicity.

no composition = no destruction;

destruction = decomposition

Monads can only be created or destructed by God.

True immortality (the personal immortality relevant for ethics) involves also memory and self-consciousness (apperception). Only spirits have this property.

The morality of human minds depends on them possessing memory and self-consciousness (for this reason they can be rewarded/punished).

  • Importance of memory for personal identity.
critique of descartes
Critique of Descartes
  • The cogito argument is a sophism.

There can be no valid inference from a state of subjective uncertainty (Descartes’ doubt) to what is objectively the case.

It is not valid to reason: “I can assume or imagine that no corporeal body exists, but I cannot imagine that I do not exist or do not think. Therefore I am not corporeal, nor is though a modification of the body”. (“Critical Comments of Descartes Principle of Philosophy” 1691: L385)

the mind body problem
The Mind-Body Problem
  • Leibniz's rejection of materialist conceptions of the mind was coupled with a strong opposition to dualistic views concerning the relationship between mind and body.
  • Leibniz criticizes Descartes’ system because it doesn’t explain how the soul can influence the body; how the mind unites with the body.
Leibniz's opposition to Cartesian dualism stems not from a rejection of unextended substances, but from his denial of the existence of genuine extended material substances.
  • To begin with, Leibniz held the Scholastic thesis that “being” and “one” are equivalent (the unity of substances).

Remember that Leibniz rejects the Cartesian notion of extended substance on the ground that it lacks unity (extended bodies are aggregates and, as such, lack unity).

Pre-established harmony

The human mind and its body have been programmed by God in such a way that they appear to interact causally with one another.

  • There is a constant conjunction. This lead philosophers to falsely believe that there is actual causality.
  • This is the denial of the mind/body interaction.
The Cartesian mind-body problem rests on the assumption that both the mind and the body are substances.

Leibniz doesn’t endorse this because, properly speaking, human bodies are not substances (they are aggregates lacking unity).

The human body, taken in abstraction from the mind, is never considered by Leibniz to be a substance (cf. Leibniz idealism).

The human body is an aggregate, thus a phenomenon. As such it is not a substance.

In his later philosophy Leibniz holds that the human body is grounded in immaterial souls or monads, but it is not itself immaterial.

So Leibniz may face a problem in understanding the mind-body union.

The doctrine of pre-established harmony has been introduced as a thesis concerning the interaction between substances (i.e. the windowless monads).
  • Thus if pre-established harmony is used to solve the mind-body union, the body should be, contrary to what Leibniz says, a substance.
Given that pre-established harmony holds among substances, we cannot validly infer that the mind is in harmony with the body, for the latter is not a substance.

We would commit the fallacy of composition.

We cannot infer from (i) what is true of the items in a group to (ii) what is true of the group as a whole.

E.g.: It would be like inferring that since Jane loves all the students in a school she loves the school.

The doctrine of the pre-established harmony could be used within Descartes’ ontology where both the mind and the body are substances.
  • Leibniz consider the world as consisting merely of one type of substance, though, there are infinitely many substances of that type.

These substances are partless, unextended entities, some of which are endowed with thought and consciousness, while others found the phenomenality of the corporeal world (Leibniz’s idealism).

Since Leibniz held that there is only one type of substance in the world, the mind and the body are ultimately composed of the same kind of substance.

Yet, he also held that mind and body are metaphysically distinct.

For any person P, P's mind is a distinct substance (a soul) from P's body.

The human mind and body are causally insulatedfrom one another.

Each of our mental states is caused by a prior state of our mind and each state of our body is caused by a prior physical state.

  • Mind/body relation

The mind “expresses” its body by perceiving it (perception is a species of expression).

  • Vs. Descartes, we have unconscious perceptions.
mind and language
Mind and Language
  • Leibniz, like contemporary cognitive scientists, saw an intimate connection between the form and content of language, and the operations of the mind.

really believe that languages are the best mirror of the human mind, and that a precise analysis of the signification of words would tell us more than anything else about the operations of the understanding (Nouveau Essays, ch.7, sec.6).

This view led Leibniz's to formulate a plan for a “universal language”. I.e., an artificial language composed of symbols, which would stand for concepts or ideas, and logical rules for their valid manipulation.

He believed that such a language would perfectly mirror the processes of intelligible human reasoning.

Leibniz came close to anticipating artificial intelligence.

Natural language

Despite its powerful resources for communication, it often makes reasoning obscure since it is an imperfect mirror of intelligible thoughts.

According to this view, cognition is essentially symbolic: it takes place in a system of representations which possesses language-like structure:

all human reasoning uses certain signs or characters. (On the Universal Science: Characteristic; G VII, 204 (S, 17))

nativism innate ideas
Nativism: Innate Ideas
  • Main argument for nativism: the human mind is causally independent from any other substance except God.

This argument is a renewal of the Platonic and Cartesian doctrine.

Like in Plato’s system, innate ideas should solve problems in the philosophy of mathematics. E.g. to explain how a priori knowledge is possible (cf. Socrates majeutics).

  • To be understood in a dispositional way.

This contrasts Descartes’ threefold conception. In particular, the material condition of ideas (i.e. ideas as acts).

To have an idea of a is to have a mental disposition to think of a when the right circumstances occur.

This contrasts with the act of thinking (e.g.: Descartes’ material condition). A disposition is not an act.

Objects of ideas, i.e. the semantics of ideas.

Ideas necessarily take possible entities as their objects.

An idea must be about a possible objects.

Thus from the fact that I can think of the round-square it doesn’t follow that I have an idea of it. For a round-square is an impossible object.

An idea in one’s mind/soul is simply another property of that monad.

This happens according to an entirely internal explanation represented by the complete concept.

But at the phenomenal level, it is no doubt the case that ideas are represented as arriving through one’s senses.

3 levels of reality

1. Metaphysical level (it includes only monads with their perception and appetition: no causality, no space, no time).

2. Phenomenal or descriptive level (what appears to be happening from the finite, imperfect perspective of the human mind).

3. Object of science (it is an illusion but in which nothing happens that is not based on what really happens in the metaphysical sphere).

Leibniz’s notion of ideas allows him to criticize Descartes’ ontological argument.

God exists if he is possible (God as the object of an idea is a possible object). It is thus a Divine privilege to need only its possibility to actually exist.

Descartes’ argument is vitiated by the assumption that we have an idea of God in Leibniz’s sense, i.e. as a disposition (and that Descartes builds God’s existence into the idea itself).

metaphysical argument for nativism
Metaphysical argument for nativism
  • Argument:

Pre-established harmony: the human mind with all other substances is causally self-sufficient.

From this + Leibniz’s theory of ideas, we should prove the innateness of all ideas.

This is reminiscent of Descartes reply to a certain Broadsheet: nothing reaches our mind from external objects …

What the argument proves is that nothing reaches the mind from outside.

Does this prove that ideas are innate?

(i) Ideas are disposition and

(ii) Dispositions are mental states.

Thus: (iii) since mental states cannot be externally caused, no idea is externally caused.

the introspection argument for innate ideas
The introspection argument for innate ideas
  • Leibniz claims that if (as Locke concedes) we assume that some ideas can be acquired from reflection (introspection), then these ideas must be innate.
  • Two criticisms of this argument

1. This only proves that an idea is not sensory- dependent in its origins: it could be formed with the formation of the mind (it rests on what we mean by “innate”).

2. It merely proves that metaphysical ideas (substance, motion, …) are innate. It doesn’t prove that mathematical ideas are innate since we don’t reach them by introspection. And mathematical ideas play a central role in Descartes and Leibniz ….

This critique is a good one. The first can be answered.

  • Answer to critique 1

The notion of reflection can be clarified in such a way that what happens in post-natal acts of reflection is that the mind first come to conscious awareness of an idea that has always been there.

nativism the argument from knowledge
Nativism: the argument from knowledge
  • Like Plato in the Meno, Leibniz thinks that we can argue for the innateness of geometrical ideas because of our capacity to know necessary truths.

See Socrates’ maieutic (the philosopher like a midwife).

Leibniz doesn’t accept, though, Plato’s theory of reminiscence, i.e. that we remember ideas/forms from a previous life.

Plato’s argument proves only a dispositional or virtual form of nativism.
  • In mathematics we make knowledge claims that it is necessarily true that p. E.g.: it is necessary true that 2+ 2 = 4.

Claims of universal necessary knowledge cannot be justified by appealing to sensory evidence.

Senses can give only instances of truth. They cannot guarantee that what happens will always happen. Senses are linked to actuality …

Innate principle play a normative role, not an explanatory one.
  • Why innate principles must be true? Why they’re not a bunch of lies?

Descartes can answer in appealing to God’s benevolence: God is not a deceiver.

Leibniz cannot answer this way since he dismisses Descartes’ appeal to God in order to solve epistemological problems.

Leibniz’s answer

Our mind is a mirror of God.

Our innate beliefs have the same structure as the eternal truths in the Divine mind.

Unlike Descartes who appeals to God’s benevolence, Leibniz appeals to the isomorphism between our min and God’s mind (monads are the mirror of God).

locke and malebranche s challenge
Locke and Malebranche’s challenge
  • They both, from different perspectives, challenge Leibniz’s view that the mind is self-contained, a self-sufficient entity.
  • Locke (book 1 of Essays)

It is not clear what the nativists are defending. Either:

(i) the view that the existence of actual knowledge and concept-possession is innate or

(ii) that the mind is born with the potential to acquire such knowledge and concepts.

1. If nativists assume (i) they are asserting something empiricallyfalse.

New-born babies show no sign of actual knowledge of necessary truths; they don’t know the truths of logic and mathematics.

  • 2. If nativists assume (ii) they say something triviallytrue.

All knowledge and concepts that one ever comes to entertain would be innate.

leibniz s defense of nativism
Leibniz’s defense of nativism
  • Leibniz claims that there is a third possibility that Locke didn’t consider.

Ideas as dispositions/potentials/inclinations/… are something less than actual knowledge. Yet, this amount to assert something more that the mere claim that the child has bare potential to understand logic etc.

The human mind, from birth, has a certain natural grain.

It is differentially predisposed toward employing certain principles and thinking in some ways rather than others.

Leibniz opposes Locke’s image of the tabula rasa.

I have also used the analogy of a veined block of marble, as opposed to an entirely homogeneous block of marble, or to a blank table, what the philosophers call a tabula rasa. For if the soul were like such a blank tablet, then the truths would be in us in the same way as the shape of Hercules is in a piece of marble when the marble is entirely neutral as to whether it assumes this shape or some other. However, if there were veins in the block which marked out the shape of Hercules rather than other shapes, then the block would be more determined to that shape, and Hercules would be innate in it, in a way, even though labor would be required to expose the veins, and to polish them into clarity, removing everything that prevents their being seen. (Leibniz NE, Preface, 52)

The disposition is more than a potential (and less than an actuality).
  • Leibniz shares with Descartes the view that dispositions play a central role in the defense of innate ideas.

We are innately programmed to shape the world in terms of things rather than cluster of features or properties. E.g. it comes more natural to us to respond to cats rather than instances of furriness. (vs. Quine’s “gavagai” example).

How can dispositions help in unpacking claims regarding mathematical and logical truths?
  • Leibniz claims that the rules of logic (e.g. propositional calculus) work within the grain of the mind.
  • How do we explain, then, than most of the time people make fallacies in their reasoning?
Malbranche’s criticism

The appeal to disposition is explanatory empty.

It falls under the very same criticism Descartes addresses to the Scholastic notion of dormitive powers. It is a circular explanation.

Cf. Fragility


fragility = the disposition to break given some circumstances …


we explain the glass breaking on the hard floor by its fragility.

The explanation is merely circular/empty; the glass brook when dropped in such circumstances because it has the property of breaking in such circumstances.

The same with a thought.

If having the idea of a triangle is a disposition to have it in such circumstances/stimulus, then one has an idea of a triangle when facing such circumstances/stimulus.

Leibniz’s possible reply (he didn’t directly address Malbranche’s critique).

Both physical and mental dispositions are grounded in non dispositional micro-structural properties of the physical/mental.

In the case of the mind the micro-structure at work are the minute perceptions. They are minute in virtue of their intensive, not extensive, magnitude. They are too low in intensity to become conscious.