According to Buddhism, things don’t have an essence that defines them. This idea is called sunyata, or emptiness. For example, you know what a car is, but is it always a car? When it is being assembled in the factory, at what point does it stop being a set of parts and become a car? One answer is that it becomes a car when it can fulfill the function of a car – that is, when it can be driven. But does that mean it stops being a car if it won’t start? What if the car’s wheels were stolen; would it still be a car? What is the essence of this thing we call “car”?
Another aspect of this idea is that things aren’t inherently either good or bad. Things may seem good or bad depending on the context, but nothing is good or bad in its essence.
Write of something you usually consider either good or bad. Then try to think of contexts where it might seem different – when something you think of as good seems bad, or vice versa.