even if tentatively, the truth of causal laws is explained in the later discussion
of induction.
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Proving Facts
Introduction
Pure technological observation simply allows humans to observe things and
occurrences that they could not observe with their unaided senses. In contrast
to this, scientific observation in the full sense of the term allows them to
observe something by causation. Chemical testing is a good example. A
scientist will add chemical X to something, a reaction will occur, the reaction
can be observed and if positive, it indicates the presence of substance Y.
The core of this process is deduction based on scientific rules. However,
while there may be certainty in principle there can be uncertainty in practice so
it is necessary to blend deduction with probability to cater for and articulate
the uncertainty.
Reasoning
Scientific evidence is usually paired with evidence based on one or more actual
observations. It can also involve one or more testings or other laboratory
processes. This is why there are two processes involved, deduction and
probability. These become intertwined, and generally the more complex the
operation the more they become intertwined.
Deduction
Deduction is involved in the operation of scientific rules. In the simple case, X
is the sole cause of Y. So, if a forensic scientist detects the presence of Y they
can give expert evidence that X occurred beforehand. In pure form this
reasoning is deductive. The syllogism takes the following form:
Major Premise
X is the sole cause of Y
Minor Premise
Y has occurred
Conclusion
Therefore X occurred prior to Y
Figure 5.14 Deduction for Inference Based on Causation
Sometimes, though, there is doubt about the components or underpinnings of
the syllogism. There may be doubt as to whether Y has occurred, there may
be doubt about universal validity of the proposed scientific rule that X is the
sole cause of Y or there may be doubt about the absolute reliability of the
testing procedure used. In this case the syllogism can still be invoked.
However, it yields only probable truth because of these doubts. Nevertheless,
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Chapter 6 Induction
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