Better Manager 7th prelims:Better Manager 7th edition

Allowing the conclusion to go beyond the evidence can also take
the form of assuming that because we are aware of the effect (the
consequent), we also know the cause (the antecedent). But this
assumption may be incorrect. An effect can have many different
causes. This fallacy of the consequent, as it is termed, can be
illustrated by the following example:

If she won the lottery she would go to the West Indies.

She has gone to the West Indies.

Therefore she has won the lottery.

ie If P then Q,

Q

Therefore P.

But there are a number of other reasons why she could have gone
to the West Indies besides winning the lottery. A clear inference
can only be drawn if the cause is directly related to the effect,
thus:

If she wins the lottery she will go to the West Indies.

She has won the lottery.

Therefore she will go to the West Indies.

ie if P then Q,

P

Therefore Q.

How to Think Clearly 299

True syllogism False syllogism

A

A

C

BC B

Figure 48.1 The difference between true and false syllogisms