I have recently taken it upon myself to dig into the wonderful world of formal logic in mathematics. Starting off with propositional logic, and quickly moving on to predicate (first-order logic), it is already striking me as a highly interesting subject. (One that can surely get very complex, and is currently still an active area of research). Although I’ve known about the topic and vaguely what it concerns for some years now, I was only properly introduced to while reading Gödel, Escher, and Bach (an excellent read, though not perhaps as revealing or ground-breaking to someone with a bit of solid background in pure mathematics and/or AI).

Now to the point of my post:  I have recently found a marvellous resource on the subject of formal logic; this website provides a gentle yet thorough introduction to both propositional and predicate logic (among other things such as set theory and recursion), along with interactive exercises. Between spending a few hours over a couple of days reading through it and a bit of discussion with someone who knows the subject has given me a pretty firm grasp of the conepts and maths behind it – at least I’d like to think. I know (perhaps foolishly) plan to go on to learn about such crazy topics as higher-order logic, categorical logic, type theory, model theory, and so on. Finding such an elucidating resource for those might be rather more challenging, though I have a few books in hand that I may review if all turns out.