1. Pick over dried chickpeas. Rinse and soak overnight in cold water with 1 teaspoon salt. Drain and rinse. Place chickpeas in a medium saucepan, and cover by several inches with fresh water. Bring to a boil, and skim off any foam. Turn heat down to medium, and simmer until tender, 35 to 45 minutes. Ten minutes before chickpeas are done, add 3/4 teaspoon salt. Remove from heat; let cool in cooking liquid for about 1 hour.

2. If using cumin seeds, toast in a dry pan over medium-low heat until they release their aroma, about 2 minutes. Let cool and grind to a powder in a spice grinder. Set aside.

3. Chop together 1/2 teaspoon salt, garlic, and 1/2 teaspoon olive oil to form a paste. Add chiles; chop to combine. Transfer to a small bowl, and add remaining oil.

4. Drain soaked chickpeas. (If using canned chickpeas, rinse.) Combine with 1 teaspoon chile mixture or to taste. Add olives, cumin, lemon juice, and salt and pepper to taste. Refrigerate until ready to serve. The salsa can be made a day ahead (return to room temperature before serving).

5. Just before serving, coarsely chop arugula, and toss with salsa.