Descartes’ project

Evidence for Descartes’ project as being one of truth: the opening principle in the Principles is concerned with what the seeker after truth must do. He must, once in the course of his life, doubt everything, as far as possible.

According to Michael Williams, Descartes was attempting to overthrow Aristotelian physics, in favour of his own mechanistic views. By making his project turn on general epistemic considerations, he could achieve his aim without explicitly facing the Aristotelian view – which many at the time would have held on to above Descartes’ new physics. As Hatfield points out, Descartes was sensitive to the prudential value of not attacking the scholastic Aristotelian position directly: it was the accepted position not just of university education, but also was strongly supported by both Protestant and Catholic orthodox theologians.

Descartes offered a new vision of the natural world: one with few natural universal laws and few fundamental properties. He denied the senses reveal the nature of substances, and held that in fact the human intellect is able to perceive the nature of reality through a purely intellectual perception – as in the wax example in Mediation II. Thus, in order to procure the fundamental truths of metaphysics, we must “withdraw the mind from the senses” and turn to our innate ideas of the essences of things.

For Descartes a necessary and sufficient criterion for true (clear and distinct) knowledge is that it is “followed by a great inclination of the will”. Such propositions are recognised by such an unshakeable inclination of the will that they cannot be challenged, even by the systematic doubt of the Meditations.

Descartes held that the human mind comes supplies with innate ideas that allow it to perceive the main properties of God (infinity and perfection), the essence of matter and the essence of mind. However, he denied that there are eternal truths independent of God’s will, and also rejected that they reflect the contents of God’s intellect. Instead, eternal truths are the free creations of God: He could have willed it that 2 + 3 = 6. However, our conceptual capacities are limited to the innate ideas God has implanted in us, and these reflect the actual truths He created.

The aim of philosophy

Descartes clearly saw philosophy as somehow prior to all other knowledge. It was the supposed to be the “foundations of physics” and all other subjects, from which other subjects could grow. For example, the order in the Principles builds up from ‘principles of knowledge’ – metaphysics – through principles of material things, to the visible universe and onto living things and man. Philosophy is like a tree, with metaphysics as the roots, the trunk as physics, and the branches as the other sciences

For example, in the Preface to the Principles, he talks of philosophy as providing ‘complete’ knowledge, encompassing “everything which the human mind is capable of knowing”.

Philosophy as ‘perfect knowledge’

“the word 'philosophy' means the study of wisdom, and by 'wisdom' is meant not only

prudence in our everyday affairs but also a perfect knowledge of all things that

mankind is capable of knowing, both for the conduct of life and for the preservation

of health and the discovery of all manner of skills.” (AT 9B:2/CSM I: 179)

Perfect knowledge is ‘deduced from first causes/principles’

“In order for this kind of knowledge to be perfect it must be deduced from first

causes; thus, in order to set about acquiring it - and it is this activity to which the term

'to philosophize' strictly refers - we must start with the search for first causes or

principles.” (ibid.)

Key features of the ‘first principles’

“These principles must satisfy two conditions. First, they must be so clear and so

evident that the human mind cannot doubt their truth when it attentively concentrates

on them; and, secondly, the knowledge of other things must depend on them, in the

sense that the principles must be capable of being known without knowledge of these

other matters, but not vice versa.” (ibid.)

The nature of ‘deduction’

“Next, in deducing from these principles the knowledge of things which depend on

them, we must try to ensure that everything in the entire chain of deductions which we draw is very manifest”.

The method of doubt

Descartes’ doubt is at each stage incomplete, requiring a more forceful argument to doubt what’s left intact:

1. Doubting the senses – leaves valid sense-data intact.

2. Dreaming argument – leaves simple and very general ideas intact.

3. Evil deceiver argument.

Michael Williams points out the Descartes smuggles in his foundationalism as early as the first meditation: ‘for convenience’, he decides not to examine each idea in turn, but instead to examine their grounds. This is contrary to Baconian scepticism, which showed that methodological scepticism need not lead to purely epistemological questions. Classical scepticism was continuing, not completable; for Descartes, on the other hand, scepticism could be complete, and yield corresponding certainty. Unlike classical doubt, Descartes’ doubt is not a mere extension of common sense.

Moreover , Williams argues, Descartes’ levels of doubt correspond to a stratification of Descartes’ epistemology, according to which the order of justification is the reverse of the order of doubt. Thus Descartes implicitly – and without justification – introduces a view of knowledge corresponding to this context- and subject-matter independent order of reasons: knowledge also has a foundational structure.

Hatfield understands Descartes’ view of how we can know as distinguishing classes of knowledge with corresponding degrees of certainty:

• Metaphysical first principles are known by the intellect acting alone, and should attain absolute certainty.

• Practical knowledge concerning...

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