Bread have a special taste or texture. At one time, all yeast-leavened breads were sourdoughs. Recently there has been a revival of sourdough bread in artisan bakeries. Traditionally, peasant families throughout Europe baked on a fixed schedule, perhaps once a week. The starter was saved from the previous week's dough. The starter was mixed with the new ingredients, the dough was left to rise, and then a piece of it was saved (to be the starter for next week's bread). The rapid expansion of steam produced during baking leavens the bread, which is as simple as it is unpredictable. Steam-leavening is
Substance theory Substance theory Substance theory, or substance–attribute theory, is an ontological theory about objecthood, positing that a "substance" is distinct from its properties. A "thing-in-itself" is a property-bearer that must be distinguished from the properties it bears. "Substance" is a key concept in ontology and metaphysics, which may be classified into monist, dualist, or pluralist varieties according to how many substances or individuals are said to populate, furnish, or exist in the world. According to monistic views, there is only one substance. Stoicism and Spinoza, for example, hold monistic views, that pneuma or God, respectively, is the one substance in the