#### Welcome to the interactive logic textbook!

Logic is a tool that helps us solve problems. Scientists use logic to figure out what theory their data supports. Mathematicians use logic to prove things like the Pythagorean theorem. Children use logic to solve Sudoku puzzles and win chess games.

You can’t learn logic without using it. That’s one reason why this textbook is interactive. You will learn about logic by applying it.

All of problems in this book are for practice. They aren’t worth points, and if you get them wrong, you get to try again. (Problem sets for your homework are not done in the textbook; your instructor will tell you where to complete those.)

Look for **key concepts** in the call-out boxes.

The point of letting you retry problems that you get wrong is so the harder you work, the more you will learn and the better you will do.

Let’s give it a try.