Major Premise
To understand the requirement that the major premise needs to be true,
consider Syllogism 2:
Syllogism 2
Major Premise
All ducks are rabbits
Minor Premise
Daffy is a duck
Conclusion
Therefore the Daffy is a rabbit
Figure 5.6 Syllogism: False Major Premise
Here the conclusion logically flows from premises, but the major premise, that
all ducks are rabbits, is not true. Consequently the conclusion is not true.
Minor Premise
To understand the requirement that the minor premise needs to be true,
consider the following example:
Syllogism 3
Major Premise
All ducks are birds
Minor Premise
A rabbit is a duck
Conclusion
Therefore a rabbit is a bird
Figure 5.7 Syllogism: False Minor Premise
Here the conclusion logically flows from the premises, but the minor premise
is not true in fact because a rabbit is not a duck. Consequently the conclusion
is not true.
Conclusion
To consider the requirement that the two premises, if true, must inevitably and
logically lead to a conclusion that is true, consider the following illustration.
For the sake of illustration we assume the minor premise, that Daffy is a bird,
is true:
Syllogism 4
Major Premise
All ducks are birds
Minor Premise
Daffy is a bird
Conclusion
Therefore Daffy is a duck
Figure 5.8 Syllogism: Illogical Reasoning
Here the premises are true in fact but the conclusion does not logically flow
from the premises. Of course, the conclusion may still be true in fact, but the
point is that it cannot be proved to be true from the premises.
 |
 |
 |