Suppose I told you I have a new car for you. And not just any car: it’s the car you’ve always dreamed of owning, in just the color you imagined it would be. Suppose I hand you the keys and tell you to take it for a spin. I think we all would agree that this would give you a kind of joy.
Now, change illustrations. Suppose you are fighting cancer. It’s a particularly aggressive cancer, with a remote chance of your survival. The treatment is brutal, with drugs and radiation that place you on the verge of death. And now the doctor walks into the room with a clipboard to deliver the news: the cancer is gone. It is not hard to imagine that you might cry. But who would doubt that those tears are tears of joy?
In both examples, the response to good news is joy, yet these joys are quite distinguishable from each other. For someone to hear that his cancer is gone and respond as though he just won a new car would indicate he is oblivious to the stakes of his situation. We don’t doubt that he is happy; we might rightly doubt that he fully understands the magnitude of both the threat he faced and the good news he has received.