With regard to the tenth book, there can be no doubt that its hymns came into being at a time when the first nine already existed. Its composers grew up in the knowledge of the older books, with which they betray their familiarity at every turn. The fact that the author of one of its groups (20–26) begins with the opening words (agnim īḷe) of the first stanza of the Rigveda, is probably an indication that Books I.–IX. already existed in his day even as a combined collection. That the tenth book is indeed an aggregate of supplementary hymns is shown by its position after the Soma book, and by the number of its hymns being made up to that of the first book (191). The unity which connects its poetry is chronological; for it is the book of recent groups and recent single hymns. Nevertheless the supplements collected in it appear for the most part to be older than the additions which occur in the earlier books.
There are many criteria, derived from its matter as well as its form, showing the recent origin of the tenth book. With regard to mythology, we find the earlier gods beginning to lose their hold on the imagination of these later singers. Some of them seem to be disappearing, like the goddess of Dawn, while only deities of widely established popularity, such as Indra and Agni, maintain their position. The comprehensive group of the Viçve devās, or “All gods,” has alone increased in prominence. On the other hand, an altogether new type, the deification of purely abstract ideas, such as “Wrath” and “Faith,” now appears for the first time. Here, too, a number of hymns are found dealing with subjects foreign to the earlier books, such as cosmogony and philosophical speculation, wedding and burial rites, spells and incantations, which give to this book a distinctive character besides indicating its recent origin.
Linguistically, also, the tenth book is clearly distinguished as later than the other books, forming in many respects a transition to the other Vedas. A few examples will here suffice to show this. Vowel contractions occur much more frequently, while the hiatus has grown rarer. The use of the letter l, as compared with r, is, in agreement with later Sanskrit, strikingly on the increase. In inflexion the employment of the Vedic nominative plural in āsas is on the decline. With regard to the vocabulary, many old words are going out of use, while others are becoming commoner. Thus the particle sīm, occurring fifty times in the rest of the Rigveda, is found only once in the tenth book. A number of words common in the later language are only to be met with in this book; for instance, labh, “to take,” kāla, “time,” lakshmī, “fortune,” evam, “thus.” Here, too, a number of conscious archaisms can be pointed out.
Thus the tenth book represents a definitely later stratum of composition in the Rigveda. Individual hymns in the earlier books have also been proved by various recognised criteria to be of later origin than others, and some advance has been made towards assigning them to three or even five literary epochs. Research has, however, not yet arrived at any certain results as to the age of whole groups in the earlier books. For it must be borne in mind that posteriority of collection and incorporation does not necessarily prove a later date of composition.
Some hundreds of years must have been needed for all the hymns found in the Rigveda to come into being. There was also, doubtless, after the separation of the Indians from the Iranians, an intermediate period, though it was probably of no great length. In this transitional age must have been composed the more ancient poems which are lost, and in which the style of the earliest preserved hymns, already composed with much skill, was developed. The poets of the older part of the Rigveda themselves mention predecessors, in whose wise they sing, whose songs they desire to renew, and speak of ancestral hymns produced in days of yore. As far as linguistic evidence is concerned, it affords little help in discriminating periods within the Rigveda except with regard to the tenth book. For throughout the hymns, in spite of the number of authors, essentially the same language prevails. It is quite possible to distinguish differences of thought, style, and poetical ability, but hardly any differences of dialect. Nevertheless, patient and minute linguistic research, combined with the indications derived from arrangement, metre, and subject-matter, is beginning to yield evidence which may lead to the recognition of chronological strata in the older books of the Rigveda.
Though the aid of MSS. for this early period entirely fails, we yet happily possess for the Rigveda an abundant mass of various readings over 2000 years old. These are contained in the other Vedas, which are largely composed of hymns, stanzas, and lines borrowed from the Rigveda. The other Vedas are, in fact, for the criticism of the Rigveda, what manuscripts are for other literary monuments. We are thus enabled to collate with the text of the Rigveda directly handed down, various readings considerably older than even the testimony of Yāska and of the Prātiçākhyas.
The comparison of the various readings supplied by the later Vedas leads to the conclusion that the text of the Rigveda existed, with comparatively few exceptions, in its present form, and not in a possibly different recension, at the time when the text of the Sāma-veda, the oldest form of the Yajur-veda, and the Atharva-veda was constituted. The number of cases is infinitesimal in which the Rigveda shows a corruption from which the others are free. Thus it appears that the kernel of Vedic tradition, as represented by the Rigveda, has come down to us, with a high degree of fixity and remarkable care for verbal integrity, from a period which can hardly be less remote than 1000 B.C.
It is only natural that a sacred collection of poetry, historical in its origin, and the heritage of oral tradition before the other Vedas were composed and the details of the later ritual practice were fixed, should have continued to be preserved more accurately than texts formed mainly by borrowing from it hymns which were arbitrarily cut up into groups of verses or into single verses, solely in order to meet new liturgical needs. For those who removed verses of the Rigveda from their context and mixed them up with their own new creations would not feel bound to guard such verses from change as strictly as those who did nothing but continue to hand down, without any break, the ancient text in its connected form. The control of tradition would be wanting where quite a new tradition was being formed.
The criticism of the text of the Rigveda itself is concerned with two periods. The first is that in which it existed alone before the other Vedas came into being; the second is that in which it appears in the phonetically modified form called the Saṃhitā text, due to the labours of grammatical editors. Being handed down in the older period exclusively by oral tradition, it was not preserved in quite authentic form down to the time of its final redaction. It did not entirely escape the fate suffered by all works which, coming down from remote antiquity, survive into an age of changed linguistic conditions. Though there are undeniable corruptions in detail belonging to the older period, the text maintained a remarkably high level of authenticity till such modifications as it had undergone reached their conclusion in the Saṃhitā text. This text differs in hundreds of places from that of the composers of the hymns; but its actual words are nearly always the same as those used by the ancient seers. Thus there would be no uncertainty as to whether the right word, for instance, was sumnam or dyumnam. The difference lies almost entirely in the phonetic changes which the words have undergone according to the rules of Sandhi prevailing in the classical language. Thus what was formerly pronounced as tuaṃ hi agne now appears as tvaṃ hy agne. The modernisation of the text thereby produced is, however, only partial, and is often inconsistently applied. The euphonic combinations introduced in the Saṃhitā text have interfered with the metre. Hence by reading according to the latter the older text can be restored. At the same time the Saṃhitā text has preserved the smallest minutiæ of detail most liable to corruption, and the slightest difference in the matter of accent and alternative forms, which might have been removed with the greatest ease. Such points furnish an additional proof that the extreme care with which the verbal integrity of the text was guarded goes back to the earlier period itself. Excepting single mistakes of tradition in the first, and those due to grammatical theories in the second period, the old text of the Rigveda thus shows itself to have been preserved from a very remote antiquity with marvellous accuracy even in the smallest details.
From the explanatory discussions of the Brāhmaṇas in connection with the Rigveda, it results that the text of the latter must have been essentially fixed in their time, and that too in quite a special manner, more, for instance, than the prose formulas of the Yajurveda. For the Çatapatha Brāhmaṇa, while speaking of the possibility of varying some of these formulas, rejects the notion of changing the text of a certain Rigvedic verse, proposed by some teachers, as something not to be thought of. The Brāhmaṇas further often mention the fact that such and such a hymn or liturgical group contains a particular number of verses. All such numerical statements appear to agree with the extant text of the Rigveda. On the other hand, transpositions and omissions of Rigvedic verses are to be found in the Brāhmaṇas. These, however, are only connected with the ritual form of those verses, and in no way show that the text from which they were taken was different from ours.