Step 1Heat the oven to 350 degrees.
Step 2Place the lentils, bay leaf, thyme and enough water to cover in medium pot. Simmer until the lentils are just tender, about 25 minutes.
Step 3While the lentils are cooking, combine the onion and vinegar in a small bowl. Let them stand 5 minutes, drain and reserve the vinegar.
Step 4Place the currants in 1/2 cup warm water to plump, 10 minutes. Drain.
Step 5Spread the walnuts on a baking sheet and toast them until fragrant and lightly browned, 5 to 7 minutes. Coarsely chop them and set them aside.
Step 6Whisk together the reserved vinegar, lemon juice, 4 tablespoons of olive oil, the mint and oregano. Season to taste with salt and pepper.
Step 7Dry the scallops thoroughly with paper towels. Season them with salt and pepper. Heat the remaining olive oil in a nonstick skillet over high heat. When the pan is hot, brown the scallops about 1 minute on each side. Remove them from the pan to a plate.
Step 8Drain the lentils and discard the bay leaf. Combine them with the onions, walnuts, currents, arugula and vinaigrette while still warm. Season to taste with salt and pepper. Arrange the lentil salad on individual plates with the scallops.