The Vedas are eternal and the source of all creations and their greatness is to be known in many different ways. As I have already stated, their sound produces in our nadis as well as in the atmosphere vibrations that are salutary not only to our own Self but to the entire world. Here we must understand "lokakshema" or our welfare of the world to mean the good of mankind as well as of all other creatures. This concern for all creation that finds expression in the Vedas is not shared by any other religion. "Sanno astu dvipadesancatuspade"-- this occurs in a mantra: the Vedas pray for the good of all creatures including bipeds, quadrupeds etc. Even grass, shrubs, trees, mountains and the rivers are not excluded from their benign purview. The happy state of all these sentient creatures and inert objects is brought about through the special quality of the Vedas.
The noble character of their sound apart, the Vedas are also notable for the lofty truths that find expression in the mantras. The tenets of these scriptures have aroused the wonder of the people of other lands, of other faiths. They are moved by the poetic beauty of the hymns, the subtle manner in which principles of social life are dealt with them, the metaphysical truths embedded and expounded in them, and the moral instruction as well as scientific truths contained in them.
Not all mantras that create benign vibrations are necessarily meaningful. In this context we have the example of the music. The alapana of a raga (the elaboration of a musical mode) is "pure" sound, that is, it has no words, but it is still is capable of producing emotions like joy, sorrow, etc. During the researches conducted by a university team, it was discovered that the vibrations created by the instrumental music quickened the growth of the plants and resulted in a higher yield. Here is a proof that the sound has the power of creation. Also to be noted is the fact that the instrumental music played to the plant does not obviously have any verbal contact--- this establishes that the sound has its own power.
The remarkable thing about the Vedas is that they are of immeasurable value as much for their sound as for their verbal content. While the sound has its creative power, the words are notable for the exalted character of the meaning they convey.
There are Tamil hymns of a very high order. To read them is to be moved by them; they touch our hearts with their intense devotion. But we have recourse only to a few of them for repeated incantation to expel a poison or to cure a disease. The authors of these hymns like Nakkirar, Arunagirinadhar and Sambandamurti have composed poems that are more moving and beautiful. But the sound of the hymns chosen for repeated incantation are potent like mantras. Among our Acharya's works are the Saundaryalahari and the Sivanandalahari. the recitation of each stanza of the Saundaryalahari brings in a specific benefit. The same is not said about the Sivanandalahari. The reason is the special mantrik power (of the sound) of the former.
There are mantras that are specially valuable for their sound but are otherwise meaningless. Similarly there are works pregnant with meaning but with no mantrik power. The glory of the Vedas is that they are a collection of mantras that are at once notable as much for the energising character of their sound as for the lofty truths they proclaim. A medicine, though bitter, does the body good, while some types of food, though delicious, do harm. Are we not delighted to have something like kusmanda-lehya, which is sweet to taste and is at the same time nourishing to the body? Similarly, the Vedas serve a two fold purpose: while they have the mantrik power to do immense good to each one of us and too the world, they also contain teachings embodying great metaphysical truths.
It must here be emphasised that on the doctrinal level the Vedas deal both with worldly life and the inner life of the Self. They teach how to conduct ourselves in such a manner as to create Atmic well-being. And their concern is not with the liberation of the individual alone; they speak about the ideals of social life and about the duties of the public. How the Brahmin ought to lead his life and how the king must rule his subjects and what ideals women are to follow: an answer to these-stated in the form of laws-is to be found in these scriptures. The Vedas indeed constitute the apex of our law-books.
For a general background, please see here