Sri Aurobindo emphasizes that the concept of avatarhood is not limited to upholding the dharma and protecting the order of society, but that it also incorporates a progressive, evolutionary element as well. Both of these aspects together are necessary roles that both define and justify the advent of an Avatar.
“But we have to remark carefully that the upholding of Dharma in the world is not the only object of the descent of the Avatar, that great mystery of the Divine manifest in humanity; for the upholding of the Dharma is not an all-sufficient object in itself, not the supreme possible aim for the manifestation of a Christ, a Krishna, a Buddha, but is only the general condition of a higher aim and a more supreme and divine utility. For there are two aspects of the divine birth; one is a descent, the birth of God in humanity, the Godhead manifesting itself in human form and nature, the eternal Avatar; the other is an ascent, the birth of man into the Godhead, man rising into the divine nature and consciousness,….; it is the being born anew in a second birth of the soul. It is that new birth that Avatarhood and the upholding of the Dharma are intended to serve.”
The Gita does not intend its statement of the Avatarhood of Krishna to become the center of a religious dogma; rather it is a profound philosophical statement of the Oneness that underlies the possibility of the conscious Divinity taking a conscious birth in a human form; and the ability of the manifested universal forms to eventually become conscious of that Oneness and Divinity within themselves.
Sri Aurobindo, Essays on the Gita, First Series, Chapter 15, The Possibility and Purpose of Avatarhood, pp. 139-140