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SCIENCE 585
two Analytics the basic Greek conception of scientific exx
planation, according to which a phenomenon was explained
when it could be deduced from general principles
or a theory
connecting it with other phenomena, just as the conclusions
ofEuclid's theorems were deduced from his axioms, postulates,
and definitions, and the conclusions of previous theorems.
Aristotle had given a generalized account of the method, and
shown that there were definite rules for
selecting premisses and
for
distinguishing between valid and invalid arguments, The
first
subjects to benefit from this new rational thinking were
theology and law; its application
to science at the end of the
twelfth century was simply the last
stage ofa general intellectual
movement, and by that time the formal structure of the new
method had been filled in with material examples from the
many specialized scientific writings translated from the Greek
and the Arabic. Of these Grosseteste had a wide knowledge,
and he saw that ifscience was to progress in his time, the primary
problems to be investigated were those of method. His own
scientific work, begun before 1209 and continuing even after
he became bishop of Lincoln in 1235, made two major con*"
tributions.
First, in commentaries on Aristotle's Posterior Analytics
and Physics he made a systematic application of logical
methods of analysis, verification, and falsification to the prob'
lems of constructing and testing scientific theories by observa^
tion and experiment. His methods can best be described by
means ofa concrete example, the attempts made by himselfand
his chief disciple, Roger Bacon, to explain the rainbow.
Grosseteste wrote several short treatises on optics, leading up to
one on the rainbow; Roger Bacon's account of the problem
appears in his Opus Majus, and follows the lines laid down by
Grosseteste. Bacon in fact gave it as an example of the experv
mental method; his Opus Majus, Opus Minus, and Opus
Tertium, all written in 1266-7, contain the chief thirteenth/*
century development of Grosseteste's conceptions of expert
mental and mathematical methods in science.
The basic problem in searching for an explanation of a