Vitalism is the theory that living things are alive because of some "vital force", some special substance or force or essence that nonliving things lack. Vitalism has been totally discredited by modern science; it is very evident from molecular biology that living things are alive because of a certain organization of nonliving matter. However, many alternative-medicine advocates propose some vitalist theory as a "theoretical justification" of their practices. Theories of qi, prana, orgone, mysterious "energies", etc.