Causes of bad reasoning Van de Lagemaat Ch 5 pp 131-139
Why do we reason poorly?
1. Laziness – too lazy to check the argument or see if there is supporting evidence
2. ignorance- easier to hold simple beliefs
3. pride – more interested in winning the argument than in establishing the truth
4. prejudice – manufacture bad reasons to justify our prejudices (this is rationalisation)
Reason and certainty
Logical reasoning is based on 3 laws of thought:
 The law of identity. If A, then A. If something is a banana, then it is a banana.
 The law of non-contradiction. Nothing can be both A and not-A. Nothing can be both a
banana and not a banana.
 The law of the excluded middle. Everything is either A or not A. Everything is either a
banana or not a banana.
Why should I be logical? - In asking for reasons, I am presupposing the value of logic. Logic is
presupposed in all meaningful communication.
Can deductive reasoning be doubted?
1. We cannot be sure that the laws of logic do not simply describe the way we think rather than the
way the universe is.
GK Chesterton (1874-1936) “Reason is itself a matter of faith.”
2. Logic depends on language in that it presupposes we can organise the world into precise,
clear-cut categories.
3. Everything is constantly changing. Nothing stays the same long enough to be identical with
itself. Then there is nothing for logic to be true of. Heraclitus (c. 540-470 BC) “You can
never step in the same river twice.”
Can inductive reasoning be doubted?
Inductive turkeys. When the farmer appears, they get fed. This happens day after day, month after
month. On 24 December, the farmer appears and kills one for Christmas dinner. Even well
confirmed generalisations can fail us.
Newton's laws of motion – confirmed by observational evidence and believed to be true for over
200 years. However, they were proven to be false.
CAN WE BE SECURE IN OUR KNOWLEDGE?
Can we justify our confidence in the comforting regularities of nature? Think back to the Truman
Show.
We cannot justify induction so perhaps we should conclude that it is simply an instinct that we share
with animals?
Using inductive reasoning is simply part of what it means to be rational.
Lateral Thinking
We can't survive without inductive and deductive reasoning but we can be trapped in the prison of
consistency – once you have taken a position on something, you may not wish to lose face by
changing your mind.
Edward de Bono (1933- ) says we must learn to think outside the box and come up with more
creative ways of looking at problems – lateral thinking.
Conclusion
We need reason to develop consistent beliefs about the world but we can sometimes become
trapped in the “prison of logic” and this can stifle our creativity. Furthermore, reason is not
appropriate in every situation and if someone is too rational, they can come across as a cold and
unfeeling automaton.
Reason needs to be balanced by emotion. [Do you think this could be the balance in the learner
profile?]