How do you know you are not evil?

Answer 1

Because you do not have red eyes.

In all seriousness, good and evil are often hard to define without guidance. Many people find that humanity is basically good, while others believe that humanity is fallen. Does that mean that humanity is evil? Not necessarily.

In most cultures, whether you are good or evil is defined by your actions. If you commit acts that are considered evil, like murder or kidnapping or rape, you may be considered evil. If you commit acts that are good, such as providing for your family, or giving to those who have less than you, or being generally helpful and charitable to others, then you will be considered good. Still for others, goodness or evil starts with your heart and mind. If your heart desires good, then you are a "good" person. If your heart desires evil things, then you may be considered "evil."