F. We notice next the second great group of Upanishads, the _Katha_, _Isā_, _Svetāsvatara_, _Mundaka_, _Mahānārāyana_,[22] which are all written in verse. That this group is later than the great prose Upanishads is abundantly clear from the changed form as well as from the more developed matter. “As contrasted with the five above-mentioned Upanishads with their awkward Brāhmana style and their allegorical interpretations of the ritual, the _Katha Upanishad_ belongs to a very different period, a time in which men began to coin the gold of Upanishad thought into separate metrical aphorisms, and to arrange them together in a more or less loose connection.”[23] Further signs of their belonging to another stage of thought are their references, more or less clear, to the Sānkhya and Yoga philosophies,[24] and their tendency to adopt the doctrine of Grace,[25] _i.e._, that salvation is not a fruit of true knowledge, but a gift of God. The idea of _Bhakti_, which became afterwards so popular, appears in this group of Upanishads only once.[26] Here also for the first time in Sanskrit literature the word _Sānkhya_ occurs as the name of a system.[27] But while these five metrical treatises are clearly later than the prose Upanishads, scholars are not agreed on the question of their relation to the great systems. Some[28] hold that the _Katha_ is earlier, others[29] that it is later, than Buddhism; Weber[30] believes that the _Svetāsvatara_, _Mundaka_, and _Mahānārāyana_ depend not only on Kapila’s system, but also on the _Yoga Sūtras_ of Patanjali (see below), while others[31] believe that in these Upanishads we have scattered pieces of teaching which were later systematized. But whatever be the truth on these points, it is clear that these five are posterior to the first group, that their relative age is _Katha_, _Isā_, _Svetāsvatara_, _Mundaka_ and _Mahānārāyana_,[32] and that this last belongs to quite a late date.[33] Along with these verse Upanishads we may take three prose works, which are manifestly still later,[34] the _Prasna_, _Maitrāyanīya_ and _Māndūkya_. G. Several centuries after the Sānkhya there appeared the Yoga philosophy, the text-book of which is the _Yoga Sūtras_. According to Indian tradition the founder of the school and the author of the Sūtras was Patanjali,[35] the well-known scholar who wrote the _Mahābhāshya_ on Pānini’s grammar. He accepts the metaphysics of the Sānkhya system, but postulates the existence of a personal god, and urges the value of Yoga practices for the attainment of _Kaivalya_, that isolation of the soul from matter, which, according to Kapila, is true salvation. Thus not one of the three main elements of his system is original; for Yoga practices have existed from a very early date in India. Yet his system is sufficiently marked off from others, first by his combination of Yoga practices with Sānkhya principles and a theistic theology, and, secondly, by his systematic treatment of Yoga methods.[36]