discourse on method
part v
descartes (1596-1650)
I. Introduction
A. Descartes's project: to establish an entirely new system of knowledge
1. this system included a mechanics that would provide a physical account of Copernican astronomy
2. his aim was
a. to demonstrate that everything in this system follows logically from an absolutely certain starting point
b. while at the same time to show that the Copernican system could actually be derived from theological beliefs
B. he suppressed the work in which he first set out to explain his system, Le Monde or Treatise on Light, because of Galileo's encounter with the Inquisition (he refers to this work in the last paragraph, which begins "I had described")
C. however, Descartes felt that he should publish some important contributions he had made to scientific knowledge, including:
1. the basis for analytic geometry
2. the inverse sine law of refraction
3. theory of the rainbow
D. these contributions were published in 1637 as the Discourse on Method, Optics, Geometry, and Meteorology
II. Mechanical Philosophy
A. his system of thought has been called the mechanical philosophy because it purports to explain everything in nature in terms of the principles of mechanics, including:
1. formation of solar system
2. nature of light
3. tides
4. prevailing winds
5 formation of mountains
6. growth of plants
B. for example, in his account of the function of the heart, he compares the pores in the blood vessels to a sieve
C. that is, he would explain everything in mechanical terms except the human mind, which he distinguishes from the minds of other animals
III. Men, machines, and animals (Discourse on Method Part V, handout from web)
A. if there were machines built to resemble monkeys or some other animal "without reason," we would have no way of distinguishing them from animals
B. However, if there were machines built to resemble us, we would have two ways to distinguish them from us:
1. use of words
a. although it is conceivable that a machine could be constructed to utter words when touched in certain places,
b. a machine cannot arrange words in response to the sense or meaning of all that is said in its presence, that is "to reply appropriately to everything that may be said in its presence" (q.v. NB: everything)
c. Problem: it is not impossible for a machine to generate an infinite number of sentences from:
1.) finite vocabulary
2.) finite set of grammar rules
d. but -- would these be appropriate responses?
2. we act from knowledge, not merely from disposition of organs
a. although machines may be able to do some things better than we can (like tell time), there will be other things that they cannot do at all
b. this shows that machines do not act on the basis of knowledge, but only from the disposition of their organs
1.) reason is a "universal instrument" that can "serve for all contingencies" (N.B. all)
2.) but machines must have a special arrangement of parts for every specific action
3.) and it is "morally impossible" -- that is, impossible for all practical purposes -- that they could have such arrangements of parts to respond to all of life's situations
c. in other words, we are not finite boxes
C. Men can be distinguished from animals in the same two ways: (next paragraph)
1. use of language
a. even the most stupid person can make him or herself understood, but not animals
b. not a question of lacking proper organs
1.) magpies, parrots can form human words, but without giving any sign that they know what they are saying
2.) while even the deaf-mutes among us can make themselves understood
c. this is evidence that animals not only have less reason than we do, but none at all
1.) little reason is needed in order to talk
2.) we notice that there are degrees of ability among animals just as there are among humans (pp. 1-2)
3.) hence, it would be incredible that even the "most perfect" of each species would not be equal to the stupidest child unless their souls were of an "entirely different nature" from ours (p. 2, q.v.)
d. ought not to confuse words with the natural signs that express emotions
e. nor can we argue that animals have their own language, for then they could make themselves understood to us (q.v.)
2. acting from knowledge
a. like machines, animals may excel us in some things, but there are other things that they cannot do at all
b. that they excel us in a few things is no proof that they have a mind, for in that case they would excel us in everything (q.v.)
c. nature acts in them according to disposition of organs -- note the analogy with a clock
D. in subsequent letters he wrote to the Marquis of Newcastle and to Henry More, the use of language became the "principal" criterion for distinguishing men from animals
IV. In conclusion to Discourse V (last paragraph)
A. our soul of a different nature than that of animals: ours is immortal
B. the Soul
1. does not arise from matter; must be specially created
2. does not dwell in human body merely like a pilot in a ship (Aristotle)
a. not only can it move the limbs of the body
a. but it is affected by what happens to it, so it must be more intimately united to its body
V. in the Discourse, part IV, Descartes also provided some metaphysical arguments regarding the distinction between the body and the soul
A. The famous “I think, therefore I am.”
B. he invited comments on these arguments, which he then received
C. the Meditations was written in reply to these objections