It might be well for all of us to remember that, while differing widely in the various little bits we know, in our infinite ignorance we are all equal. - Karl Popper
So yesterday we had the fourth evening of this twelve session course. I posted on the third session last week. What we covered is illustrated on the Powerpoint handouts I gave out as two six-slides-to-a-page handouts. Click on slides 1-6, Powerpoint or slides 1-6, PDF and slides 7-12, Powerpoint or slides 7-12, PDF to see.