Reason and TOK: What is deductive reasoning?
Posted on : 12-12-2011 | By : admin | In : Ways of Knowing
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This is the Monty Python ‘witch scene’ from ‘The Holy Grail’– an entertaining clip where you can spot the multiple flaws in reasoning!
Deductive reasoning is any form of reasoning that moves from the general to the particular.
Here are three examples of syllogisms which contains two premises and a conclusion:
Premise 1: Typically men earn more money than women.
Premise 2: I am a man.
Conclusion: Therefore I earn a lot of money.
Premise 1: I am human and I’m heterosexual.
Premise 2: You are a human.
Conclusion: You are heterosexual.
Premise 1: I am an IB student.
Premise 2: All IB students suffer from an unbearably large workload.
Conclusion: Therefore I must suffer from an unbearably large workload.
The arguments move from a general claim in premise 1 to a particular conclusion. In order for the conclusion to be true, both premises must be true and the argument must be valid. In the final example about IB students, you might consider the truth of premise 2 (few would dispute this!) and whether the argument valid?
You may want to invent your own syllogisms to try out different variations of true and untrue premises and valid and invalid arguments.
When you think about syllogisms consider:
1. Are both premises either true or not true?
2. Is the argument valid/ invalid?





