An introductory text-book of logic - Mellone, Sydney - Rare Books at ...

238 THE GENERAL NATURE OF INDUCTION.
Ex. I.
Fever-stricken patients are excessively thirsty ;
This patient is excessively thirsty ;
Therefore he is fever-stricken.
Formally, all enthymemes in fig.
ii. are invalid, for they
attempt an affirmative conclusion ; but practically they
are of extreme importance.
"
" The sign or
"
"
symptom
is not conclusive, for it might have another cause; but
the conclusion has a certain probability. And when we
have a number of independent symptoms all suggesting
the same conclusion, we regard the conclusion as prac
tically certain. In legal investigations, a
"
"
coil of
circumstantial evidence consists of nothing else than a
series of enthymemes in fig. ii. For example : a person
is found in an uninhabited house, dead from the effects
of a wound; and on that same evening, a man, A.B., is
seen running away from the neighbourhood of the house.
Ex. 2.
Murderers flee from the scene of the crime ;
A.B. flees from the scene of the crime ;
Therefore A.B. may be the murderer.
This, by itself, is of course very inconclusive. But if,
when A.B. s house is searched, it is found that his
clothes are blood-stained, then we may make another
enthymeme in fig. ii., with conclusion pointing in the
same direction.
Similarly with other items of evidence
e.g., A.B. s boots fit the fresh foot-marks going from
the house where the murder was committed; and so
on. Many times a group of such enthymemes has
led, rightly or wrongly, to the execution of a prisoner.
The following examples afford tentative justifications
of what is suggested by the last two examples in fig.
iii. :