# Example exercises and answers for predicate logic inference (+ FOL in general)

## Main Question or Discussion Point

I'm battling with first order predicate logic (no identity, no extensions) and currently esp. inference using the so called "natural reasoning" rules for inference.

Now, the text book we use, is very ambiguously defined, even I have spotted several 'errors' in it, the lecturer even more.

This makes learning formal systems quite hard for me, as I don't always grasp things, if they are not accurately defined.

Also, the examples for doing inference are terse. There are only a few and they are the simplest of forms. Most of what I would consider 'recurring patterns' of partial inference are not covered. Absolutely no heuristics are given, even the simple ones that I've been able to come up with myself.

Hence, I've been doing progressively more difficult inferences for my course now for four weeks.

But now I've hit a wall.

I have tried, re-tried, slept a day, re-tried, started over, taken a fresh approach, chunked the problem to smaller parts, etc.

No dice, can't get this weeks exercises solved. I could barely muster last weeks after two days of trying, but I did them. Not these.

I'm not yet willing to accept that this stuff is too difficult for me to learn by myself and that I should just give up.

But I suspect there are things I've misunderstood or not properly understood, hence my difficulty in applying the rules of inference.

Now my question:

Does anybody know of any source, free or for-pay, for learning logic (incl. FOPL esp. doing inferences and the proofs for major theorems) that has plenty of self-study examples including full step-by-step answers and even explanations.

I'm not (too) afraid of formalism, but I need the fluffy natural language explanations too.

I guess I'm just slow (being dyslexic doesn't help), but I'm not yet willing to give up.

It's just that I think I've hit a wall with what I can extract from our very thin course book and I need an additional source.

Anyone?

All pointers appreciates.

As background, I'm an adult student getting back to math & phys after 15 year break and really starting over from basics. Some uni basics level linear algebra, computability and discrete maths + extensive high school maths, but that's it and it's 15 years ago. So no book is _too_ simple for me :)

PS Naturally I've done very extensive google/msn/yahoo searches but I've have found quite little of what is really useful for doing inferences. Quite a lot of definitions using various notations styles, but examples have been really simple, and absolutely no heuristics, no answers to difficult questions and very few examples altogether.

Related Set Theory, Logic, Probability, Statistics News on Phys.org

The following books were recommended:

A Friendly Introduction to Mathematical Logic, Christopher C. Leary, out of print
[sorry, not allowed to posts urls yet]

I'll post more for others' benefit, if I get them.

I will, thanks.