Being alive means being in a body, and being in a body means being separated from all other bodies. And being separated means being alone. This is true of every creature, and it is true of man more than any other creature. He is not only alone; he also knows that he is alone he is aware of what he is. Therefore, he asks the question of his aloneness. He asks why he is alone and how he can overcome his being alone. He cannot stand it; but cannot escape it either. It is his destiny to be alone and to be aware of it. It's his greatness that he is centered within himself. He is separated from his world, and able to look at it. Only because this is so, he can know the world, and love and transform it. Only he who is alone can claim to be a man. This is the greatness, and this is the burden, of man.
Thus, the wisdom of our language has created the word loneliness to emphasize the pain of being alone, and it has created the word solitude to emphasize the glory of being alone.
— Paul Tillich