(p. 59) added 5, Professor Haug (Brahma und die Brahmanen) 1 6, making a sum total of 170. New names, however, are constantly being added in the catalogues of MSS. published by Bühler, Kielhorn, Burnell, Rajendralal Mitra, and others, and I shall reserve therefore a more complete list of Upanishads for a later volume.
Though it is easy to see that these Upanishads belong to very different periods of Indian thought, any attempt to fix their relative age seems to me for the present almost hopeless. No one can doubt that the Upanishads which have had a place assigned to them in the Samhitâs, Brâhmanas, and Âranyakas are the oldest. Next to these we can draw a line to include the Upanishads clearly referred to in the Vedânta-sûtras, or explained and quoted by Saṅkara, by Sâyana, and other more modern commentators. We can distinguish Upanishads in prose from Upanishads in mixed prose and verse, and again Upanishads in archaic verse from Upanishads in regular and continuous Anushtubh Slokas. We can also class them according to their subjects, and, at last, according to the sects to which they belong. But beyond this it is hardly safe to venture at present. Attempts have been made by Professor Weber and M. Regnaud to fix in each class the relative age of certain Upanishads, and I do not deny to their arguments, even where they conflict with each other, considerable weight in forming a preliminary judgment. But I know of hardly any argument which is really convincing, or which could not be met by counter arguments equally strong. Simplicity may be a sign of antiquity, but it is not so always, for what seems simple, may be the result of abbreviation. One Upanishad may give the correct, another an evidently corrupt reading, yet it does not follow that the correct reading may not be the result of an emendation. It is quite clear that a large mass of traditional Upanishads must have existed before they assumed their present form. Where two or three or four Upanishads contain the same story, told almost in the same words, they are not always copied from one another, but they have been settled independently, in different localities, by different teachers, it may be, for different purposes.
