POCKET bread presents a philosophical dilemma. Like doughnut holes, the major culinary contribution is inherent in nonexistence. The inedibility of the pocket is the very essence of its usefulness.

But scientifically, the pocket in pita bread is less mysterious. It's a product of extremely high heat forcing the air to expand and the bread to rise quickly, so that gluten strands snap through the middle. The hot oven causes the "loaves" to puff dramatically and collapse subsequently on the pocket enclosed.

Whole-wheat pita bread, while delicious, is crumbly and tends to fall apart easily. Fastidious eaters might think that ultimate reliance on knife and fork defeats the purpose of the pocket, but those in search of flavor resign themselves to mess. The situation is eased but not eliminated by keeping pocket contents to a minimum.

Falafel (which has a number of spellings so keep an open mind when you look for it in a cookbook index) is Middle Eastern snack food. The falafel and pita combination is as classic as hamburger and bun. Its tahini spread resembles a rich sesame mayonnaise.

Pita bread fillings offer more options than the conventional sandwich creations. Pockets are perfect for holding sloppier fillings that you wouldn't dream of putting between two slices of bread. Chunky salads and runny vegetables in sauces become neat entre'es in pockets. Of course bologna is acceptable, but not nearly as interesting.

If you pack pockets for lunch, put the filling in a separate container to keep the bread fresh. For dinner, fill cloth-lined baskets with pita bread, set out several bowls of different fillings and invite your friends for a fill-your-pockets buffet. % PIZZA SALAD (6 servings) 8 ounces canned tomato sauce 3 tablespoons olive oil 1/4 cup red wine vinegar 1 teaspoon dried oregano 2 cloves garlic, minced 1/8 teaspoon freshly ground black pepper 14 ounces canned artichoke hearts, drained 8 ounces mozzarella cheese 6 ounces provolone cheese 1 pint cherry tomatoes 10 good-quality ripe olives, pitted and chopped 1 cup cooked garbanzo beans, drained of any liquid 1 tablespoon fresh parsley, minced Shredded lettuce 6 large pita bread halves or 6 small pita bread rounds

In a jar, combine tomato sauce, olive oil, vinegar, oregano, garlic and pepper. Shake well to combine and set aside. Quarter the artichoke hearts and place in a medium-sized bowl. Shred or chop well the mozzarella and provolone cheeses and add to bowl. Wash and quarter the cherry tomatoes; add to bowl along with olives, garbanzo beans and parsley. Toss well. If possible, marinate several hours or overnight. Serve in pita bread with lots of shredded lettuce. FALAFEL (6 servings) 5 cups cooked, drained garbanzo beans 1 large onion, minced 1/4 cup minced parsley 1 tablespoon cumin seeds 2 teaspoons ground coriander seeds 1 tablespoon lemon juice 1/4 teaspoon cayenne pepper 2 eggs 1/4 cup whole-wheat flour Vegetable oil for frying Pita bread Tahini Spread: 5 cloves garlic 1/2 cup tahini (sesame paste) 1/2 cup freshly squeezed lemon juice 1/3 cup water Salt to taste

Chop garbanzo beans until they resemble coarse bread crumbs (this is most efficiently done in a food processor or blender). Add onions and parsley. Toast cumin seeds by shaking them over medium heat in a dry skillet. They will begin to smoke and give off an aroma. Grind them in a mortar and add them to the garbanzo beans. Crush coriander in mortar and add to beans. Add lemon juice and cayenne pepper to beans. Beat eggs lightly and add to beans, along with flour. Stir to blend well. Heat about 1 inch of vegetable oil in a large skillet. Make small patties (about 3 inches in diameter and 1/2- to 3/4-inch thick) of the garbanzo bean mixture. Fry in hot oil until brown on both sides and drain on absorbent paper. Serve in pita bread, with tahini spread and shredded lettuce, if desired.

To make the sauce, crush the garlic cloves and mince. Place in blender or food processor with tahini and blend well. Add lemon juice in a stream, blending all the while. Then add water in a stream. Salt to taste. RATATOUILLE (6 servings) 2 tablespoons olive oil 1 large onion, sliced 3 cloves minced garlic 4 cups mushrooms 2 green peppers 1 pound canned plum tomatoes 2 zucchini 1 medium eggplant, cubed 1 teaspoon basil 1 teaspoon oregano 1/4 cup vinegar 1/2 to 1 teaspoon freshly ground pepper Salt to taste Pita bread halves

Heat olive oil in large dutch oven. Add sliced onion and garlic and cook until wilted. Add whole mushrooms (halve them if they are very large) and stir over high heat about 4 minutes. Reduce heat and add seeded, chopped green peppers. Drain tomatoes and reserve liquid. Add tomatoes to vegetables. Trim and slice zucchini and add to pot. Trim and cube eggplant (without peeling). Add to vegetables along with basil, oregano, vinegar, pepper and salt to taste. Simmer about 20 minutes. Correct seasoning. Serve warm or at room temperature with pita bread halves.