deduction. Deduction proclaims the Rule, R, that A causes B. It then asserts
that if A has occurred, B will also occur. Abduction observes B, then derives
the existence of the Rule R asserting that A causes B. In other words,
abduction is the process of explaining how things came to be as they are.
To emphasise this, abduction can be explained by a diagram that specifically
refers to Rule R:
Observation
B has occurred
Explanation
A causes B
Strength of Explanation
No other explanation explains B as well as Rule R that says:
“A causes B”.
Conclusion
Therefore, Rule R that says “A causes B” is probably correct.
Figure 4.7 Form of Abduction
This diagram makes clear the relationships between abduction and Rule R.
Abduction is like induction in that it
establishes the likelihood that Rule R is
correct without conclusively demonstrating that it is correct.
Analogy
Analogy involves arguing
from
the known similarities between two things, X
and Y, to the existence of further similarities between them. With analogy, Rule
R determines the attributes or properties of X and Y.
Premise 1
Rule R says: “X has attribute A”.
Premise 2
X is similar to Y
Conclusion 1
Rule R says: “Y has attribute A”.
Conclusion 2
Rule R says: “Both X and Y have attribute A”.
Figure 4.8 Form of Analogy
Depicting analogy in this form with Rule R reveals clearly the effect of arguing
by analogy. Arguing by analogy expands the scope of Rule R. This forms a
neat contrast with abduction, which establishes the existence of Rule R.
Summary
This analysis of and comparison between the various forms of reasoning
involves the following:
(1)
There are two events, A and B.
(2)
There is a rule, Rule R. Rule R says A causes B. Thus, where there is A
there will be B.
Each of the various forms of reasoning is doing something with Rule R. What
each form of reasoning does with Rule R can be summarised in the following
table:
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