#### 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.

That's one reason why this textbook is interactive. You will learn about logic by using it.

There are two types of problems in the book. **Practice problems** are mixed into each section. They are there to help you learn: they aren't worth points, and if you get them wrong, you get to try again.

[**Note for UW students in Winter 2019**: ignore this next part about exercise problems and homework grade. All your homework is done in Canvas. Don't forget to do it!]

**Exercise problems** occur at the end of the chapter. They help you extend your understanding and combine ideas learned in different sections. The exercise problems count toward your homework grade, but you can retry those problems as well, up until the due time set by your instructor.

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

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

Let's give it a try.