A progressive evolution of the involved divine consciousness is the nature of life in the material world. The ancient sages recognized that there are five Purushas, or “Beings” active in humanity, with each one founded in and based upon one of the sheathes or bodies in this evolutionary structure. The first of these five, is the physical being, which, as the name implies, is closely tied to the physical body and under control of the forces and activities of the material world. Even when the life force emerges and gains strength, representing the vital being, or when the mind develops, representing the mental being, those individuals who are rooted in the physical being are predominantly acted upon by the material world and this colors their vital and mental efforts as well.
Sri Aurobindo describes it thus: “This physical soul is present everywhere in material Nature; it pervades the body, actuates obscurely its movements and is the whole basis of its experiences; it informs all things even that are not mentally conscious. But in man this physical being has become vitalised and mentalised; it has received something of the law and capacities of the vital and mental being and nature. But its possession of them is derivative, superimposed, as it were, on its original nature and exercised under subjection to the law and action of the physical existence and its instruments. It is this dominance of our mental and vital parts by the body and the physical nature which seems at first sight to justify the theory of the materialists that mind and life are only circumstances and results of physical force and all their operations explicable by the activities of that force in the animal body. In fact, entire subjection of the mind and life to the body is the characteristic of an undeveloped humanity, as it is in an even greater degree of the infra-human animal.”
As long as the soul remains under the predominant control of the physical being, it will take births that conform to the need to work out the issues at that level, until such time as it is prepared to move to the predominant action of the next level. “According to the theory of reincarnation those who do not get beyond this stage in the earthly life, cannot rise after death to the mental or higher vital worlds, but have to return from the confines of a series of physical planes to increase their development in the next earthly existence. For the undeveloped physical soul is entirely dominated by material nature and its impressions and has to work them out to a better advantage before it can rise in the scale of being.”
Sri Aurobindo, The Synthesis of Yoga, Part Two: The Yoga of Integral Knowledge, Chapter 20, The Lower Triple Purusha, pg. 442