My old secondary school, Silverdale, (a comprehensive) encourages its brighter pupils to study science subjects, and generally there is a culture that the humanities are the soft, easy option. This goes right through to A-level; when it comes to applying to university, of those who apply to Oxbridge maybe 90% apply to Cambridge because it is viewed as being better for science. The brightest GCSE students do triple science, getting a GCSE in each of Biology, Chemistry and Physics, and to fit this in they only have one hour of R.E. a month and one hour of P.S.H.E. a month too, alternating between these two in a one hour slot on the school’s biweekly timetable. This is actually illegal, as they’re supposed to have I believe an hour a week of R.E.

My old philosophy teacher was discussing these lessons with me, and his hopes that since they’re not doing an R.E. GCSE (the best GCSE), he might as well teach them some philosophy, and he’s been doing ethics and the like, but it’s viewed as a soft subject again and he wanted to engage them with something that would appeal to them. We came up with Logic, something I’ve already gone into the school to talk about before (but to sixth formers), and so today I went in to talk to a Y11 class about premises, conclusions and validity.

It went pretty well and a good few of them really did get what we were talking about, which was great, and the majority certainly had some idea. The most difficult thing is how you can tell people what validity is. Explaining how you can write an argument as consisting of premises and a conclusion is fine, but then to tell them what validity is you have to give a fairly formal definition, and formal definitions are scary and, coming all at once as they tend to do, overwhelming. But neither Paul or I could come up with a way to tell them what validity is other than defining it, repeating it over and over and writing it up on the board.

The hope was to get some non-science into them and we probably succeeded. One example one girl came up with involved humans being 70% water, Jesus walking on water and her being capable of walking on humans, which leads to the conclusion that the girl was 70% Jesus. Pretty sure it’s invalid.

Here’s our lesson plan notes:

Ridiculous symbols on the board.

Theatre: Money exchange

What is wrong with Sean’s sentence: “Some bank notes are forgeries. So, for all we know, they all are forgeries.” ? (on board) Write up suggestions.

Answer: if all bank notes are forgeries then there can’t actually be any bank notes.

Actually Sean is making an argument - note the “if…then”. Are there other arguments where something like this happens? Wouldn’t it be great if we had tools to detect when this sort of thing happens? Anxiety-inducing. Similar mistakes in other cases. Teachers might make mistakes like this and no-one would notice and people would learn the wrong things.

This is the study of the logic of the argument. PMB bigs it up.

Basic tools to help us do this: premises and conclusions. Circles on the board. Then write up Socrates syllogism.

Validity tells us if an argument is okay.

An argument is valid is when; if the premises are true, the conclusion must also be true.

It is raining outside. If I do not wish to get wet when it is raining, I need an umbrella. I do not wish to get wet, I need an umbrella.

Some vampires are bloodthirsty. Some werewolves are bloodthirsty. Therefore, some vampires are werewolves.

THINK OF SOME VALID AND INVALID ARGUMENTS in pairs. Write on board, vote valid/invalid.

Need 10 minutes for this. Gosh isn’t this brilliant. Surely we can apply this to every single argument and it’ll work. BUT THEN (Sean), I’ve a final example for you: The moon is white. Anything white is made of cheese. We conclude that the moon is made of cheese.

Every good argument is valid but not every valid argument is good.

Everything we’ve done today is philosophy. Also underpins computing.