Jonathan Rée

Analytical Contents

Chronological Table 15
Introduction 17


The young Descartes thought he was destined to revolutionize science.    19
Empiricists, however, find it hard to understand what Descartes hoped to do.        20
This is because they ignore the relativity of explanation, i.e. the fact that the way something is explained determines how it can be described, and vice versa. Descartes’s philosophy was an attempt to indicate which ways of describing things were scientific. 21
Descartes’s theory of science was reductionist. It said that science should describe the world in terms of ‘simple natures’ and ‘composite natures’, and show how the latter could be reduced to the former.23
This can be seen as a special form of subsumptive explanation, i.e. explanation of the specific in terms of the general.25


Descartes is famous for his work in algebra.  28
He illustrated algebraic operations with geometrical diagrams.28
His innovations made it possible to solve many algebraical problems which had formerly been regarded as insoluble.30
Descartes thought physical science could be regarded as a branch of mathematics.31
By this he meant (a) that physical science is only concerned with the measurable properties of things and (b) that the algebraical technique of representing each variable in a problem by a special symbol should be used in physics to show the dependence of composite natures on simple ones. 32


Descartes called the process of identifying the simple natures in complex phenomena analysis.35
He stated that analysis ought to concentrate on what is absolute, i.e. what contains the simple natures in a relatively uncomplicated form.36
Absolutes were universal (i.e. ubiquitous) because (physical) simple natures were properties of every particle.38
The sorts of classifications which Descartes recommended were based on several basic categories (corresponding to the simple natures), whereas the ancient subsumptive classifications were based on a single supremely general category.40
Descartes excluded from physical science all explanations in terms of purpose, or in terms of irreducibly specific, as opposed to universal, properties.41
Although he did not take much interest in organized scientific observation or experiment, his reductionist ‘mechanical philosophy’ was an integral part of the seventeenth-century revolution in physical science.43


Cartesian physics rapidly became well known.46
It seemed to explain things in terms of the stuff they were made of, i.e. to provide compositional explanations. Compositional explanations have to be in terms of what is substantial in the sense of being a quantity which tends to be conserved. In effect Cartesian physics seemed to analyse physical phenomena as mixtures of matter and motion.46
Descartes’s laws of nature apply conservation principles to motion   in a straight line.48
Descartes never said that motion was substantial—perhaps because he thought this would imply that space and time are absolute.49
Descartes thought the notion of vacuum was illusory, and that matter was identical with space.51
This led to the theory of vortices which was meant to explain both gravity and planetary motions.52
The denial of vacuum made momentum practically unmeasurable, and indeed made nonsense of the whole idea of a science of matter and motion.55
Newtonian physics eventually superseded Cartesian physics; but it stood in the Cartesian tradition.57


Descartes thought that the sense organs, nerves and brain formed a purely physical system centred on the pineal gland.61
He thought that in the case of human beings this gland contained something non-physical—the soul. (The ‘homunculus’ concept of the soul.)63
In his early writings, Descartes claimed that the soul perceives and acts only on certain states of the brain, which he called ‘ideas’.64
In the works of some later philosophers this concept of ideas developed into the empiricist theory of mind (or ideas).65
This theory could not serve the purposes for which Descartes designed the concept of ideas.68


Descartes’s philosophy changed considerably in about 1630.70
Descartes’s late philosophy is based on the method of doubt, a technique for identifying the essences of things. 70
The method of doubt corresponds to analysis.73
Descartes tried to identify the essence of the soul, beginning with the cogito, which shows that it is senseless to doubt that one is thinking.73
The concept of mind differs from that of the soul in that it is closely associated with that of thought.75
Descartes argued (a) that one can doubt the existence of everything except one’s mind without doubting the existence of one’s soul and   (b) that it followed that the mind is identical with the soul (the idealist definition of the soul).76


The Platonistic dualism of sensory and intellectual knowledge was almost universally subscribed to up to Descartes’s time.77
Descartes relied on it in some early writings.77
But in his late writings he rejected it.79
This led to two enormous advances in the theory of knowledge:
(a) Descartes came to treat ideas as mental rather than physical, and this enabled him to disentangle the notion of ideas from the empiricist theory.
(b) Descartes generalized the notion of ideas, and this enabled him to use it in explaining both intellectual and sensory knowledge, and   thus to undermine the Platonistic dualism.83


According to the Platonistic interpretation, scientific knowledge85
has to do with the intelligible (perhaps divine) world rather than with the sensible world. 
Descartes rejected this Platonistic interpretation.  86
Descartes thought that the distinctive feature of scientific knowledge was that it involved ideas which were clear and distinct.87
Descartes thought that the distinctive feature of scientific knowledge was that it involved ideas which were clear and distinct.87
Descartes’s principle of clarity and distinctness says that if we have a clear and distinct idea of something, it is possible for it to exist.88


Descartes thought that ordinary descriptions of human action and perception are confused, and ought to be replaced by ones which clearly separate people’s mental and physical states.91
His theory of mind was reductionist, as opposed to pluralist: he believed that all mental phenomena could be reduced to thinking, i.e. to the combined operation of the ‘faculties’ of intellect and will. This was an anti-Platonistic doctrine in that it implied that the mind is involved even in experience of physical particulars.92
Descartes tried to define the mind in terms of certain knowledge; but it is wrong to assimilate his account to superficially similar pluralist ones.94
It is also wrong to criticize Descartes’s account for being narrowly intellectualistic.97


The standard objection to Descartes’s dualism of mental properties and physical ones is that it cannot accommodate the interaction of mind and body. But the objection is invalid: Descartes’s physics was reductionist, but not determinist, and this allowed him to think that the mind, though not physical, could affect the body.100
The Cartesian materialists were a group of empiricists who rejected Descartes’s dualism while retaining his homunculus concept of the soul.102
Descartes perceived the inadequacy of this type of materialism. Mental properties are a type of structural property, and as such they cannot be accounted for by a reductionist physical science.103
Dualism and the homunculus concept are hardly compatible with each other, but Descartes believed in them both.105


Descartes rejected both the idea that the soul is physical and the idea that it is a substantial form.108
Descartes based his own concept of the soul on his dualism of mind and matter and his idealist definition of the soul.109
The first stage of Descartes’s argument for his concept of the soul was an attempt to prove the conceivability of idealism, i.e. of the view that nothing exists except thinking.110
Descartes then asserted that if idealism were true, this would cast no doubt on the existence of the soul. But he was mistaken: at least it would east doubt on orthodox views about the individuality of souls.112
Leibniz and Spinoza developed Descartes’s concept of the soul in ways which illustrate its inadequacy.113
Descartes called the mind or soul a substance. He thought mental substances had a pure but inexplicable individuality.114
Descartes mistakenly thought that he had proved that souls can be disembodied and must be immortal.116


Descartes’s claim that a person's essence is thinking need not lead into difficulties about individuality.118
Descartes’s claim implied that a person is active (and therefore free) only when his behaviour is a necessary consequence of his being a thinking thing.119
But Descartes’s account of human actions and passions was ambiguous between (a) a homunculus account and (b) a dualist account. As (a) it identifies actions with any behaviour caused by thinking; as (b) it identifies them only with (expressions of) thoughts which flow from the essence of the soul.121


The rise of capitalism was associated with attempts to divide people’s inward life from their external attributes.124
The new introjected concept of the self was extensively deployed in the works of empiricist thinkers.125
It has a strong influence on conceptions of mental health, especially those developed by the Cartesian materialists.126
They thought the cause of madness was that the self lost control of external behaviour. This made it possible for them to regard madness either as due to reprehensible weakness or as something external to the madman.128
The empiricist version of the new concept of the self (unlike Descartes’s version) made the self systematically elusive.129
Descartes’s concept of the human mind is often dismissed as facile. This view is certainly supported by some of Descartes’s remarks.130
Descartes’s definition of the mind in terms of certain knowledge was mainly a refusal to accept the empiricist account of mind, rather than a refusal to believe in the unconscious.131
The apparent ‘objectivity’ of mental states can be explained without recourse to empiricism.132
Freud’s account of the mind is not flatly incompatible with Descartes’s.134


Descartes called the property of ideas in virtue of which they can represent things objective reality; and claimed that with most ideas, one could specify their objective reality without implying that anything existed corresponding to them. But he thought that this was not true of the idea of God.135
Descartes’s causal argument says that there is a ‘first idea’ which is the idea of God, and whose objective reality must be caused by something outside the realm of thought. This argument relies on an obviously unacceptable conception of reality.
The ontological argument restates Descartes’s case by saying that it follows from the definition of God as a being ‘to whose essence existence belongs’ that God exists.
Descartes’s basic argument is: (a) we have the idea of God as something which could not conceivably not exist, and (b) it follows that God exists. (b) is often rejected on the inadequate ground that things like the existence of God cannot be proved from ‘mere ideas’. The vulnerable part of Descartes’s argument is (a). It seems that all Descartes can mean by ‘God’ is ‘reality’.138


Descartes’s early philosophy was sceptical.141
Later, Descartes tried to disprove scepticism. His argument from God’s benevolence says that God could not be so malevolent as to deny to humans the ability to obtain knowledge. This argument seems circular, and in any case is invalid.141
Descartes’s case against scepticism contained two other elements: (a) the theory of innate ideas, which says that men are naturally endowed with clear and distinct ideas (and, incidentally, provided him with an account of the inner self).142
And (b) the theory of the creation of eternal truths, according to144
which God had created the ‘eternal truths’, which corresponded to innate ideas. This doctrine did away with the Platonistic separation between knowledge of eternal truths and knowledge of ordinary things. 
Descartes’s humanistic theory of knowledge is the main thesis of his late philosophy.146
Descartes’s humanism dehumanized God.148
Descartes’s statements of his humanism were unavoidably chaotic.150


In the seventeenth century, Cartesianism was popular and persecuted.151
Descartes’s supreme reputation in the early eighteenth century was gradually eclipsed by Newton’s.153
The habit of classifying thinkers into warring schools has resulted in a completely mistaken image of Descartes.156
Appendix 1  Simple Natures159
Appendix 2  The standard criticisms of Descartes’s Argument for the Existence of God162
Notes 165
Select Bibliography197
Index 201


The Inner Self

In the sixteenth and seventeenth centuries, as capitalism began to establish itself in Europe, new forms of consciousness and new theories of human nature came into being. It became normal for people to think of themselves as equal competitors in a commodity market, rather than as having a natural place in a God-given social hierarchy. Regardless of rank, people increasingly came to ‘recognise in each other the rights of private proprietors’. [1] Even the labouring poor were proprietors, with a native endowment of property in the form of their ability to work, or labour power. As Locke said, ‘Every man has a Property in his own Person . . . The Labour of his Body, and the Work of his Hands, we may say, are properly his.’ [2] Individuals were connected with a social framework only by means of commodities, and Hobbes said, ‘A man's labour also is a commodity exchangeable for benefit, as well as any other thing.’ [3] Labour, or rather labour power, was external to the individual, and human freedom consisted in the opportunity of selling one’s labour power to anyone who was prepared to buy it. Luther (1483-1546) had said, ‘The soul will not be touched if the body is maltreated and the person subjected to another man’s power.’ [4] In this way the possessive individualism of the new social order divided the individual’s private, inward life from his external, social attributes [5] and led to an unprecedented privatization or introjection of human experience. [6]

Possessive individualism has had a profound influence on systems of morality. Protestantism, for instance, tended to make moral virtue a matter of inner conscience and private spiritual struggle. Luther, as the young Marx put it, ‘liberated man from exterior religiosity by making man’s inner conscience religious. He emancipated the body from chains by enchaining the heart.’ [7] Similarly the subjectivists and moral-sense theorists


of the eighteenth century thought that the way to find out what was right and wrong was to look ‘into your own breast’ [8]; the romantics thought that the highest virtue was to be true to one’s private, inner experience [9]; and the utilitarians tried to base morality on private feelings of pleasure and pain. [10] Thus the rise of capitalism was accompanied by an increasing preoccupation with individual subjectivity. [11]

Descartes’s division of mental operations into actions and passions was part of this process. It was in effect an attempt to divide a person’s thoughts into ones which expressed his real, inner nature and ones which did not, and to identify within the individual’s mind a central core of true personality, a self, an inner self, or an ego, which could be distinguished from accidental accretions. Truly free human actions were ones which issued from this source. [12]

This introjected notion of the self remained only implicit in Descartes’s writings. It was taken up and developed, however, by numerous empiricist writers. They required the notion because their habit of treating people’s ideas as a sort of external world, or as objects which are acted on and perceived, made it necessary for them to think of a person not so much as a homunculus inside the body, but rather as a homunculus inside the mind (see above, pp. 65-68). They thought of the mind as inside the body, and of the self as inside the mind.


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[Descartes and History]

Since the eighteenth century, histories of philosophy have tended to classify philosophers into opposing ‘schools’, which are supposed to have agreed about what the basic problems of philosophy are, but to have proposed opposite solutions to them. As a result, the possibility that in the course of history philosophers have contributed to a progressive enlargement of theoretical understanding has been completely lost from sight.

The modern image of Descartes is a product of this general view of the history of philosophy. Newton and Descartes have come to be seen as representatives of quite opposite schools of thought. The Newtonian school, often referred to as ‘empiricism’, is supposed to hold that scientific knowledge is obtained only by the patient and painstaking collection of facts; and the Cartesian school, often referred to as ‘rationalism’ or ‘a priorism’, is supposed to have tried to skip this hard work and to dream up pleasing theories based on whimsical generalities.

The writer of a history of philosophy has to interpret not so much the personality of the philosopher, even his intellectual personality, as the focus and form of his system, and even less to dwell on psychological minutiae and subtleties; he has rather to separate what is definite, the permanent and genuine crystallisations from the proofs, the debating points and the philosopher’s own presentation, in so far as these are self-conscious; he has to separate the ever advancing progress of true philosophical knowledge from the wordy exterior consciousness of the subject, a progress which manifests itself in so many forms and is the stuff and energy of those developments.

Karl Marx [23]


Modern historians of science, even if they acknowledge that Descartes made extremely important contributions to science, tend to present him as an example of ‘the ambitious scientist hoping to get from his own head and from a few a priori principles the whole of science’. [24] And a typical historian of philosophy says of Descartes that in the field of science ‘no real discovery of any kind stands to his credit’, and says that in Descartes’s theory of science, ‘physical existence ceases to be relevant: what matters is conformity to mathematical type. Actuality yields to possibility, fact to formula, and we are embarked on the fatal sea of the a priori.’ [25] This modern image of Descartes has almost completely obliterated the old view that he was the founder of the ‘new philosophy’, whose work was carried on by Newton and later scientists; but it is the old view which is closest to the truth. The principles of the ‘new philosophy’, and the theory of know ledge and the theory of human nature which go with it; the concepts of an idea, of mathematical laws of nature, and of a world which is not supervised by a personal God, are so fundamental to modern consciousness that it is hard not to regard them as part of the natural property of the human mind. But, in fact, they are a product of the seventeenth century, and above all of the work of Descartes.


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[Selected boxed quotations]

All science would be superfluous if the outward appearance and the essence of things directly coincided.

Karl Marx [14]



They [the thinkers before Descartes] . . . laid it down as an axiom that judgements of God far surpass human understanding. This doctrine might have concealed the truth from the human race for all eternity, if mathematics, which is concerned not with final causes but with the essences and properties of figures, had not provided them with another standard of truth.

Spinoza [19]


Philosophy first builds itself up within the religious form of consciousness, and in so doing on the one hand destroys religion as such, while on the other hand, in its positive content, it still moves only within the religious sphere.

Karl Marx [38]




14  Capital, vol. III, ch. 48, p. 817.



1  Karl Marx, Capital, vol. I, part 1, ch. 2, p. 84.

2  Second Treatise of Government, section 27.

Leviathan, ch. 24.

4  ‘On Christian Liberty’, quoted in Hegel’s Philosophy of Right, section 48.

5  ‘The division between the personal and the class individual, the accidental nature of the conditions of life for the individual, appears only with the emergence of the class, which is itself a product of the bourgeoisie’, Marx and Engels, The German Ideology, edited by C. J. Arthur, Lawrence & Wishart, 1970, p. 84.

6  Many of the ideas of this paragraph come from C. B. MacPherson’s The Political Theory of Possessive Individualism, especially pp. 48-9, 142.

7  ‘A Contribution to the Critique . . . Introduction’, McLellan, ed., Early Works, p. 123.

8  ‘Take any action allow’d to be Vicious . . . The vice entirely escapes you, as long as you consider the object. You never can find it, till you turn your reflection into your own breast. . .’ Hume, Treatise, III i 1.

9  ‘I coddle my heart like a sick child and give in to its every whim. . .’ Goethe, Sorrows of Young Werther, Book I.

10  ‘Nature has placed mankind under the governance of two sovereign masters, pain and pleasure. It is for them alone to point out what we ought to do. . .’ Bentham, Fragment on Government, ch. 1, section 1.

11  These themes are well discussed in Lionel Trilling’s Sincerity and Authenticity, Oxford University Press, 1972, especially ch. 1I. See also Ian Watt, The Rise of the Novel (1957), Penguin Books, 1963, ch. 6, especially pp. 180-83.

12  I am using, the word ‘self’ as a name for the subject of such actions. The self might be called the ‘tautological subject’ of such acting, just as the


actions are its tautological object. Similarly, a winner is the tautological subject of winning, and a win or victory is its tautological object.


19  Spinoza, Ethics, Book I, appendix.


38  Theories of Surplus Value, Vol. I, p. 52.


23  ‘'Dissertation and Preliminary Notes’ (1839). Early Texts, pp. 21-2.


SOURCE: Rée, Jonathan. Descartes. New York: Pica Press, 1975. (London: Allen Lane, 1974.) 204 pp.

Philosophy and Its Past
by Jonathan Rée, Michael Ayers, Adam Westoby

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On the Jackson Trail” by Peter Osborne

Descartes & Marxism: Selected Bibliography

Intellectual Life in Society, Conventional and Unconventional, & Related Topics:
A Bibliography in Progress

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