Wash and cube unpeeled eggplant. Salt and let stand 1 hour. Squeeze dry. Saute in oil until soft. Remove. Saute onions and garlic in same oil. Add tomatoes, olives, and celery. Cook until tender--15 minutes. Add eggplant, capers, and pine nuts. In another pan heat vinegar and sugar. When dissolved, pour over eggplant. Season to taste and cook an additional 20 minutes. Serve hot or cold as relish with dinner or with french bread rounds as a buffet or cocktail dish.