The Year 7 Scholars led by Dr Burling were building on the work done in Philosophy and Theology, where they have been considering deductive reasoning. They are familiar with the notions of a valid argument, one in which the conclusion must follow from the premises and a sound one in which the conclusion must follow from the premises AND the premises are true. So:
- All dogs living on Mars eat Jelly.
- Baxter (Mr Cavendish’s dog) lives on Mars
Therefore, Baxter eats jelly. (This is valid but not sound.)
This form of reasoning deals in certainty: the conclusion MUST follow from the premises, as certainly, as the old adage goes, as night follows day… But how do we learn the premises of our deductions? And how certain can we be however when the final stage of our reasoning is not the result of a deduction, but of a different sort of reasoning or logic i.e. Induction?
Using examples from Socrates to Peppa Pig, Dr Burling first refreshed the students’ knowledge of deductive reasoning using Venn diagrams. He then moved them on to the new territory of Inductive reasoning or, as Aristotle put it, “how we know general truths from particular experiences.” So,
- Everyone I have seen is mortal
Therefore everyone is mortal.
The problem here, as Hume put it, is that this kind of reasoning is not a valid deduction and so experiences cannot get you any certainty about general truths, no matter how many you have. Predicting the future from the past can be a dangerous game: however, many times you have observed something does not guarantee its future occurrence. As Bertrand Russell said, “the man who has fed the chicken every day throughout its life at last wrings its neck instead, showing that more refined views as to the uniformity of nature would have been useful to the chicken.”