Heat oil2 tablespoons in a large stockpot over medium-high heat.  Add onion1 and sauté for 4 minutes, stirring occasionally.  Add carrots2 and celery2 and sauté for an additional 3-4 minutes, or until the carrots are softened a bit, stirring occasionally.  Add garlic4 cloves and sauté for an additional 1-2 minutes, or until fragrant, stirring occasionally.  Add chicken stock8 cups, rosemary3 sprigs, thyme3 sprigs and sage1 sprig, and gently stir until combined.  Continue cooking until the soup reaches a simmer.