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René Descartes (1596-1650): An Architect of the Modern Age

 A. The “Father of Modern Philosophy”

Descartes is still rightly called the father of modern philosophy, not in the sense that our present-day belief systems lamely follow the Cartesian model, but in the richer and more interesting sense that, without Descartes’ philosophy, the very shape of the problems with which we still wrestle, about knowledge and science, subjectivity and reality, matter and consciousness, would have been profoundly different.
                                                                                                                                       —John Cottingham

Descartes’ almost canonical status has led to his thought being assimilated to a range of very different philosophies, and put to a wide variety of different and often incompatible uses. More than any other modern philosopher, he has been fashioned according to the philosophies of the time and interpreted accordingly, a fashioning that places him at the roots of particular modern developments, and has often created images of a particular persona. Although the idea of Descartes as the ‘father of modern philosophy’ is, I suspect, one that has its origins in nineteenth-century historiography of philosophy, it is undeniable that he has had a pivotal role in philosophical thinking since the middle of the seventeenth century.

                                                                                                                                        —Stephen Gaukroger (1995)

René Descartes (1596-1650) is usually considered the founder of modern philosophy, and, I think, rightly. He is the first man of high philosophic capacity whose outlook is profoundly affected by the new physics and astronomy. While it is true that he retains much of scholasticism, he does not accept foundations laid by predecessors, but endeavors to construct a complete philosophic edifice de novo. This had not happened since Aristotle....

                                                                                                                                       —Betrand Russell (1945)


I.A Epistemology: Traditional Problems

1. What is the basic nature of human knowledge? How should we define knowledge? What are its essential components?

Standard preliminary definition:
Knowledge is justified true belief.

The traditional view, originating in Plato’s Meno and Theaetetus, actually addresses a particular type of knowledge, propositional knowledge: Person S knows that p (where p is some statement or proposition) is the case, i.e., that p is true. Propositions make an epistemic (knowledge) claim or assertion that is strictly either true or false (truth-value). They are the objects of propositional knowledge.

Sample Propositions

  • Jesse “the mind” Ventura is governor of Minnesota
  • Columbus crossed the Atlantic in 1900
  • Every event has a cause
  • A bachelor is an unmarried male
  • Water freezes at 32º F

Propositional knowledge: Preface the above propositions with “I know that...”

Conditions of propositional knowledge:

a) The belief condition
b) The truth condition

  • correspondence
  • coherence
  • pragmatic utility

c) The Justification Condition

  • epistemic foundationalism
  • epistemic coherentism

2. Kinds of Knowledge:

a) Propositional Knowledge

Type Standard Objects
empirical (a posteriori) physical objects
nonempirical (a priori)  logical, mathematical truths


Empirical Nonempirical
Water freezes at 32 degrees F 10+10 = 20
Extraterrestrial beings exist  No statement is both true and false
René Descartes was French All bachelors are unmarried males

b) Acquaintance Knowledge: Person S knows X (something or someone) by means of direct, immediate experience (objects in the world, our sensations, personal beliefs and desires, etc.).


  • I know my cat very well
  • I know I admire altruistic acts

c) Competence Knowledge: Person S knows how to do X. Practical skill knowledge or know-how.


  • You know how to get around the East side of Providence
  • You know how to drive a car
  • You know how to speak English
  • You know how to use a computer

3. Sources of Knowledge: Traditional Candidates

  • sensory experience
  • memory
  • reflective introspection
  • reason
  • testimony

4. The Scope and Limits of Knowledge

  • skepticism
  • relativism
  • universalism

I.B) Descartes’ epistemology

Autonomy: self-conscious, deliberate attempt to conduct epistemological inquiry independent of traditional authority or personal prejudice (preconceived opinion).

Radical Foundationalism: certain, indubitable knowledge is justified on the basis of a fundamental first principle that becomes the foundation for our entire edifice of derived knowledge.

Subjectivity as epistemological starting point: Perhaps the most striking and revolutionary feature of Descartes’ epistemology is its radically subjective point of departure. In contrast to the classical orientation to objectivity (external objects, nature, or reality), Descartes seeks to reconstruct knowledge ‘from the inside outwards,’ i.e., from introspective certainty of one’s own subjective consciousness to knowledge of the external world.

Rationalism: the primary source of knowledge is reason, conceived as our cognitive capacity to acquire truth independent of (a priori) sensory, empirical experience.


A. Autonomy: Advances a strictly philosophical employment of reason independent of faith, external authority, religious sources, and institutional coercion. Rejection of the Scholastic, Medieval distinction between faith and reason as two independent sources of knowledge. In the Medieval period faith functions as the fundamental framework within which reason operates. Augustine (354—430 AD) typifies this epistemological division in his famous dictum: credo ut intelligam (I believe in order to understand).

Mechanistic Model of Scientific Explanation: Rejection of the Aristotelian, teleological model of explanation based on final causes. A final cause is the purpose or goal that causes something to occur.

health is the final cause of exercise; God is the final cause of everything that occurs. This explanatory model reflects the premodern, traditional subordination of physics to theology. Descartes substitutes a mechanistic framework in which fundamental mathematical and physical principles govern matter in motion.