It is a generally recognized concept in psychological circles, that we are circumscribed and limited by the frame within which we see and understand things. We have the power to act within that frame, according to the terms and definitions of that frame; and any inherent conflicts, limitations or contradictions cannot be reconciled as long as we remain fixed within that framework.
Sri Aurobindo points out that the need to defend the Dharma, the way of life that prevails in the world or a particular society, is something that can be done using the powers already in existence in that society, through the instrumentality of the leaders, the wise sages, philosophers and teachers, or the warrior kings of the age. The advent of the Avatar is therefore not sufficiently justified solely by an intense difficulty facing the world or the social order.
It is true that an extreme crisis of society may point to a need to move beyond the circumscribed limits and be truly solved only by advancing to the next evolutionary stage; therefore, such a crisis may actually be the sign and call for the action of the Avatar.
If we look at the great beings who have been considered Avatars, whether Christ, Krishna, Buddha, Rama, we see a transformative action to introduce a new principle into the way and the action of the world; and we see an awareness by that individual of his seminal role in the introduction of that new principle.
Sri Aurobindo states it succinctly: “The Avatar comes as the manifestation of the divine nature in the human nature, the apocalypse of its Christhood, Krishnahood, Buddhahood, in order that the human nature may by moulding its principle, thought, feeling, action, being on the lines of that Christhood, Krishnahood, Buddhahood transfigure itself into the Divine. The law, the Dharma which the Avatar establishes is given for that purpose chiefly; the Christ, Krishna, Buddha stands in its centre as the gate, he makes through himself the way men shall follow. That is why each Incarnation holds before men his own example and declares of himself that he is the way and the gate; he declares too the oneness of his humanity with the divine being, declares that the Son of Man and the Father above from whom he has descended are one, that Krishna in the human body….and the supreme Lord and Friend of all creatures are but two revelations of the same divine Purushottama, revealed there in his own being, revealed here in the type of humanity.”
Sri Aurobindo, Essays on the Gita, First Series, Chapter 15, The Possibility and Purpose of Avatarhood, pp. 140-141