To further substantiate the "I think therefore I am argument" consider this: if I didn't exist neither would you or any of existence itself. From my perspective, your existence nor anyones has any meaning without mine. If I didn't exist there would be no meaning to any of human, plant, animal, or even the entire universe. And when I die, it will remain the same FROM MY PERSPECTIVE. Same goes for everyone else, unless everything is just a product of my consciousness.