俱舍論疏 28.38

28.38

The Śāstra says: "These four fundamental [...] are established with the name 'formless.'" This states the similarities and differences. Among these four formless attainments, because the upper three preparatory stages do not take material form as intentional object, they are called 'eliminating the ideation of material form.' The preparatory stage of the sphere of infinite space, because it takes material form as intentional object, is not 'eliminating the ideation of material form.' However, although the four fundamental attainments and the four preparatory stages differ in their taking or not taking material form as intentional object, because they all lack material form, they are equally called 'formless.'