To sum is to add a bunch of one(s) together.
After a long day of forced toiling, forced mingling with dimwitted fellow slaves, and other stuff, this particular slave just wanted to be alone, for a change. Why? To be lost in himself. Because the self, especially his, was his alone. It still is mine, he shouted to himself. I am I, and they can never change that! But, the night soon ended, and the slave worked once more, for another day, and the day after that, and the next as well. Soon, the solitude was filled with the anguish of another day, and nights became too short for any real, meaningful, conversations. To chatter away silently in the dim light of a lamp was all he ever wanted. But he needed to eat, a place to sleep, warmth, company, and love. Without these, the solitude would wither away. He knew this, because he was smart. So, he toiled with no other way. Because the Other was here to stay.