**edit: 29 Mar, the compact proof truth table for modus ponens needed “2”, not “1” under column 7.**

I think this will be the first of three posts on logic. In this one, I will look at truth tables and at using them to prove tautologies (valid logical propositions).

(If I had known how much typographic trouble this post would cause…. Well, after a little practice with the new symbols, it wasn’t so bad.)

I expect that the second post will deal with “quantifiers “, namely “there exists” and “for all”, and their classical or linguistic counterparts, “some”, and “all”.

And the third post should deal with Aristotle’s syllogisms. They started it all — for me in particular, and for the world in general. All I wanted to do when I started was review the syllogisms given what little I knew of modern logic. It turns out there’s a major difference between Aristotle and modern logic, largely motivated I think by the explicit idea of the empty set. We’ll see the difference in principle in the second post, in practice in the third.

As usual, I’m not trying to write an introductory text here, just picking out a few things that interest me.

## Introduction

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