No you are not the only person in the universe. Because number 1, who is writing this, an animal, robot, or person? And number 2, if you're just "imagining" it, how could you imagine this website? Or your parents? Or you teachers? Or Albert Einstein? You can't imagine other people because then you can't imagine yourself. I mean, seriously, how can you imagine your parents when they gave birth to you? It doesn't make any sense. And if you really think you're imagining other people, then you're imagining Jesus, God, Allah, Ganesh, or whatever god you believe in. But if it is your belief that you're "imagining everybody" then you can stick with that. I'm not trying to be rude or argue about anyone's beliefs, but I'm just saying that it is absolutely impossible to imagine other people.