Sri Krishna will tell us also in the Bhagavad Gita that the highest action of the Divine is loka-saṁgraha; loka-saṁgraha means: saṁgraha means to keep unity; loka means people. To keep people united is the highest action of the Divine, which is the same thing as Dharma; loka-saṁgrahārthāya, or dharma-saṁsthāpanārthāya, they have the same meaning: to keep people together, and to establish Dharma are the same thing. Whenever therefore, there is a danger of the dissolution of the society, of people, they are breaking ground, saṁbhavāmi yuge yuge, “I come from time to time”.
But why from time to time? Once he comes and Dharma is established, why should He come again and again? The reason is that this world is an ascending world. This why Sri Krishna says: cātur-varṇyaṁ sṛṣṭaṁ mayā: this world is an ascending movement. Therefore, this sentence is very important. Because this world is a movement in which there is an ascent step by step, in which human beings are asked to run, and attain to the perfection by Knowledge, they will not be able to ascend truly, they will not attain to the supreme divine Knowledge, unless a true Knowledge is given to them. Because there is an ascending movement, therefore even when Dharma is established, and people are held together, the moment you make a further step of ascent, the previous will break down. In this sense you might say that Dharma is a progressive development.
Just as there is sanātana dharma, there is an eternal law, which holds everything; there is also what you may call yuga-dharma: the Dharma which is ready for this yuga. It is not sanātana dharma, it manifest something of it but it is not full sanātana dharma: it is yuga-dharma. Whenever Divine comes on this earth, He establishes Dharma, but it is yuga-dharma: it is enough for that moment, because this world is an ascending movement. The moment there is a farther ascent, that Dharma will again decline, and the society will again go down into breaking point; therefore there will be a need for the Supreme to come again, and to manifest a higher Dharma.
In the concept of India, the Avatar Himself evolves, and evolves by marking specific points of ascent. There is the concept that the first were the animal Avatars: matsya, varāha, kūrma, these are the animal births, but the divine births. Because in each case that particular evolutionary movement had reached a critical point, even to manifest a fish in a physical form out of pure waters was an extremely difficult task. It was the big jump: from water to create a form was a very big jump in the evolutionary movement.
Whenever there is a great jump to make, which the present (whatever is manifested) is not able to do, whatever is manifested tends to remain with the law of that particular movement. The Dharma of the present species cannot lead you to move beyond your species. At the most, you can perfect your species and its capacities; but to move beyond and yet you need to go beyond, it is a world of ascent; the world is an evolutionary movement. When you have to move forward from one level of evolution to a higher level of evolution, which is beyond the capacity of the given species, then, the Divine manifests, and takes up the whole burden of evolution, and concentrates the difficulties of the present in their acutest form, and in the same form in which others are struggling, shows how while remaining in that form, you can still work out an ascent. Not like a miracle saying that, “Look I can be different from you”. The same form is kept, accepts all the difficulties of that form, and through that He makes a kind of a passage, He digs a tunnel as it were, and shows how you can move from that lower level to a higher level.
And then, from animal forms we have the idea of vāmana Avatar: a human form but in a dwarf form. And then the paraśhu rāma, the Rajasic man followed by Sattwic man that is Sri Rama, and then Sri Krishna, the perfect divine human being. And kalki will manifest the fullness of Krishna-hood you might say. All that Krishna wanted to manifest, the full manifestation of Sri Krishna, so that Krishna consciousness spreads over the whole world fully, becomes generalised, just as today the human consciousness is generalised all over the world.
The most undeveloped human being and the most developed human being, they all have one thing common into them: capacity to add, subtracts, multiply, and divide. Whether they do arithmetically or otherwise, but this is a natural tendency in all the human beings. You do not need to teach anybody, basic arithmetic; even a child when he is given a little, he knows that he needs more. That something is taken away; he understands it is taken away: subtraction, (or division or multiplication). This is generalised all over the humanity.
Similarly something of Krishna consciousness, when it is generalised that is the aim of evolution. Ultimately mad-bhāvam āgatāḥ, what is the divine nature, the divine nature should be spread and generalised in mankind, and that is the Indian idea of kalki. Once that is done, there is no need of an Avatar because the aim of Avatar is only to lead you towards that, and once that is done, then, there is no further need; it is already given; it is an open book: there will be no blockade. The divine birth is needed to break the blockade, to dig out a tunnel, but when all the tunnels are opened up for the divine manifestation, then there is no need of an Avatar. That is why in the Indian concept, we have not one Avatar, but a series of Avatar needed, and also culminating point of Avatar, after which there is no need of an Avatar.
If you want to summarise the whole thing that we have said is that there is in this world a law of ascent, and a law of descent. Man continues to ascend, and the Divine continues to descend in response to ascent.