Heat oil in a large, wide frying pan over medium high heat. Add celery and cook until tender, stirring often. Remove celery with a slotted spoon and reserve.
Place eggplant in the pan, reduce heat to medium and cook until eggplant is lightly browned and tender, stirring often. Add onion and continue cooking and stirring until onion is soft, but not browned. Use the slotted spoon to remove the eggplant and onion and add to reserved celery.
Place vinegar, sugar, tomatoes and water in the pan and cook over medium heat, stirring for 5 minutes. Return the other cooked vegetables to the pan. Stir in capers, olives, raisins and parsley; reduce heat and simmer, uncovered for about 20 minutes more. Taste and add oregano, salt and pepper as you like it. Remove from heat and cool. Cover and refrigerate until needed. Serve at room temperature, spread on crackers, spooned onto crisp lettuce leaves or use as a side dish with just about anything. makes 6-8 servings.