A Historical Introduction to the
Philosophy of Science

Ch. 5: Affirmation and Development of Aristotle's Method in the Medieval Period

Book cover: A Historical Introduction to the Philosophy of Science by John Losee

The following is a summary of the fifth chapter of John Losee's book, A Historical Introduction to the Philosophy of Science (fourth edition), with some ancillary notes.

Philosophers discussed in this chapter: Robert Grosseteste (c. 1168–1253); Roger Bacon (c. 1214–92); John Duns Scotus (c. 1265–1308); William of Ockham (c. 1280–1349); Nicolaus of Autrecourt (c. 1300–after 1350)

[p. 27] From 1150, Aristotle's works on science and scientific method gained greater authority from being translated into Latin.

[p. 28] Aristotle's ideas dominated European thought for the next three centuries.

The Inductive–Deductive Pattern of Scientific Inquiry

Robert Grosseteste and Roger Bacon repackaged Aristotle's inductive–deductive loop as the 'Method of Resolution and Composition':

  • inductive stage 'resolution' of phenomena into constituent elements
  • deductive stage = 'composition' in which elements are combined to reconstruct the original phenomena

E.g., Grosseteste applied this procedure to explaining spectral colours.

[pp. 28–9] For Roger Bacon, the 'Method of Resolution and Composition' requires active experimentation to collect all relevant facts (e.g., breaking a magnetic needle to create two new magnets [p. 29]) [Bacon's 'Second Prerogative'].

[p. 29] To add to Aristotle's inductive procedure, Grosseteste suggested the inductive Method of Difference to test for causal power (e.g., administer test herb in situations where no other purgative agent is present). This principle was later adopted as 'Mill's Joint Method of Agreement and Difference' [LA: John Stuart Mill in the 19th Century].

[pp. 29–30] John Duns Scotus also added the Method of Agreement in which combinations of circumstances are examined for a common circumstance concomitant with a particular effect. Duns Scotus claimed this method can only show 'aptitudinal union' (regularity) and not causal necessity as God can intervene at any time to produce a different effect. William of Ockham agreed.

[pp. 30–1] William of Ockham's Method of Difference allowed in an ideal case that a cause can be established from a single test in which two sets of circumstances are identical except in one case a particular circumstance is present with the effect and in the other that circumstance is absent along with its effect. In practice, it's very difficult to be sure that the two sets of test circumstances are identical except for that one particular circumstance.

Evaluation of Competing Explanations

[p. 31] Grosseteste and Bacon, following Aristotle, recognized that an effect can be deduced from more than one set of premises.

They recommended that at the end of Aristotle's inductive–deductive procedure, further testing be done to new situations [Bacon's 'First Prerogative'].

[pp. 31–2] Freiberg in the 14th Century applied this method in his experimental setup testing his theory of rainbows. He successfully reproduced a secondary rainbow with reversed colours and the 11 degree separation between primary and secondary rainbows.

[p. 32] Grosseteste and Bacon often ignored their own advice for further experimentation, relying instead on a priori [prior to experience] deduction.

Grosseteste suggested applying a deductive method of falsification to eliminate competing hypotheses that entail the same effect.

If hypothesis H entails consequence C and it is discovered that C is not the case, then conclude that hypothesis H is false.

If H then C;   not C      therefore not H      (modus tollens)

Book cover: Philosophy of Science: An Historical Anthology by Timothy McGrew, Marc Alspector-Kelly and Fritz Allhoff

[p. 33] Grosseteste used the modus tollens form of argument in an attempt to disprove the hypothesis that the sun generates heat by conduction. But his attempted falsification failed because his stated consequence C (adjacent celestial matter undergoes a change of quality) was not shown by him to be false.

Although other philosophers and mathematicians used the modus tollens form of argument, Grosseteste was the first to apply it systematically. The method of falsification also became very influential (e.g., John Buridan) [p. 34].
[LA: This method of elimination became the cornerstone of Karl Popper's famous philosophy of science born in the 1940s known as 'Falsificationism'.]

[p. 34] Grosseteste also defended the principle that nature always chooses the simplest path. William of Ockham thought this principle limited God's power and so recommended the criterion of simplicity (later known as 'Ockham's Razor') for formulating concepts and constructing theories. He used this principle to eliminate the concept of 'impetus' in referring to moving bodies.

The Controversy about Necessary Truth

[p. 35] Aristotle thought that the first principles of the sciences are (a) self-evident and (b) necessarily true (could not be otherwise).

John Duns Scotus argued that first principles are necessarily true simply in virtue of the meanings of the words (granting that by sense experience we must first learn the meanings of the words) (e.g., 'opaque bodies cast shadows' is necessarily true.)

For Duns Scotus, there are two types of necessary truths:

  1. first principles and their deductive consequences
  2. statements of aptitudinal unions of phenomena (e.g., all ravens can be black)

For Duns Scotus, empirical generalizations are contingent truths (e.g., all ravens examined have been black).

[p. 36] For Duns Scotus, contingently true generalizations must be deduced from first principles. (e.g., 'Opaque bodies cast shadows' and 'Earth is an opaque body between sun and moon' entails 'Moon is frequently eclipsed'.)

Nicolaus of Autrecourt rejected Aristotle's and Duns Scotus' view that the first principles of the sciences (from induction) are known with certainty (i.e., are necessarily true).

[pp. 36–7] Nicolaus restricted certain knowledge to the combined premises and conclusion of a deductive argument (e.g., If A and B and C, then A) and to articles of faith. A deductive argument is valid if and only if asserting the premises and denying the conclusion is a contradiction.

[p. 37] As valid deductive arguments reveal no new information that was not already in the premises, Nicolaus argued that scientific demonstrations do not show necessary causal relations between cause and effect. Inductive arguments and statements about causes do not entail that a correlation between two events will hold in the future.
[LA: Nicolaus' arguments expressing uncertainty about necessary causal relations gains a big foothold with David Hume's famous skeptical argument against causal necessity in the 18th Century.]

Questions to Consider:

  1. What were the chief contributions to the development of the scientific method in the medieval period?
  2. Does the method of falsification decisively knock out a competing theory from further consideration for all time?
  3. Are causal relations necessary, and, if so, in what sense?

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