  Most Nyāya-Vaiśeṣika texts are structured in one of two ways. They either follow a traditional Vaiśeṣika pattern, in which the categories and their various sub-groups are discussed in order, or else they follow a pattern employed by the Buddhist logician Diṅnāga, and copied by Gaṅgeśa, in which each of the sources of knowledge is treated in turn. The Manual of Reason, however, adopts a style of analysis due to Vātsyāyana (the first commentator on the Nyāya-sūtra). Vātsyāyana stated that: