Trim the raw artichoke down to the heart. Using a spoon, scrape out the fuzzy choke and discard.
You can also peel the stem and use that in the soup, since the stem is an extension of the heart. When your artichokes are clear of fuzz and outside petals, roughly chop the raw heart. Wash and roughly chop rest of the vegetables.
Heat the oil in a large thick-bottomed pot. Sweat (to sauté without color) the artichokes, onion, leek, garlic, celery and thyme, until tender. Add the chicken or vegetable liquid stock. Gently simmer the soup for 20 minutes.
Add the roughly chopped sourdough bread and sage. Simmer 3-5 minutes more. In small batches, purée the soup until smooth using either a blender, food processor or immersion blender. Place all of the soup into a clean saucepan, reheat, and check seasoning.
(Use caution when using canned or packaged broth as they can contain a lot of sodium.) Season with fresh ground black pepper. Enjoy!