Geoscience Reference
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cycle of inductions and deductions. Van Bemmelen (
1961
) referred to this approach
as the prognosis-diagnosis method of research.
The Logic of Scientific Discovery
is the title of an influential topic by Popper
(
2002
) of which the German Edition was published in 1934 and the first English
Edition in 1959. Popper (
2002
, p. 3) explains that a scientist, whether theorist or
experimenter, puts forward statements or systems of statements and tests them step
by step. In the field of the empirical sciences, which would include geology, the
scientist constructs hypotheses, or systems of theories, and tests them against
experience by observation and experiment. Popper opposed the widely held view
(e.g., by F.W.J. Schelling and G.W.F. Hegel; and also by I. Kant and F. Bacon) that
the empirical sciences can be characterized by the fact that they use inductive
methods only. Instead of this Popper advanced the theory of “the deductive method
of testing” in that a hypothesis can only be empirically tested and only after it has
been postulated. Demarcation by falsification is an essential element in Popper's
approach. However, we have to keep in mind the role played by probability theory
in which falsification does not necessarily result in rejection of a test hypothesis.
Instead of this, the end conclusion may be a relative statement such as “there is
more than a 95 % probability that the hypothesis is true”. Because of the great
uncertainties and possibility of multiple explanations, geoscientists should proceed
in accordance with the axioms of the theory of probability as they were advanced,
for example, by Kolmogorov (
1931
) as will be discussed in more detail in the next
chapter. It is a remarkable feature of geology that a theory that turns out to be true as
proven by irrefutable evidence often was already assumed to be true much earlier
by some geologists when conclusive evidence did not yet exist. Examples of this
form of anticipation previously discussed in this chapter were the origin of ice ages
(Kroll), plate tectonics (Staub), and continental drift (Wegener).
1.2.4 Quality of Predictions
The question of how good is your prediction is continuously asked in the
geosciences, particularly in economic geology. For example, in the oil industry it
is known from experience that most holes, especially the wildcats, will remain dry.
Nevertheless, the geologist is asked to provide an opinion as to whether it is
worthwhile drilling a hole at a particular site. This problem has been discussed in
detail by Grayson (
1960
) and de Finetti (
1972
). The geologist does not have any say
in the final decision of whether or not to drill. This is the responsibility of the
decision-maker who will reach a conclusion after considering all different pieces of
information available of which the geologist's report is just one piece. The geolo-
gist cannot state categorically that oil is present or absent. Neither can she restrict
herself to a mere listing of reliable facts. A conclusion about the probable outcome
of the drilling is precisely what the geologist is called upon to provide. Grayson
(
1960
) found that most geologic reports contain probabilistic answers that are
disguised in vague adjectives (“fairly good prospect”, “favorable”, “permissive”,
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