In the chapter on "What is Practical Theosophy?" in The Key to Theosophy, Madame H. P. Blavatsky names reincarnation as one of the four links of the Golden Chain that should bind humanity into one family, one Universal Brotherhood.

The practical application of the teaching about reincarnation is something that each of us should consider, especially if we are interested in the amelioration of such social conditions as are adverse to the healthy and harmonious development of our fellow beings.

First, let us consider the relationship that exists between ourselves as reincarnating entities or egos and all the other egos whom we meet in our present incarnation and who collectively form the brotherhood that we refer to as the human family. Intellectually, we may perceive this Brotherhood to be a fact, but full realization of it can only come when we live as brothers in our daily life.

As reincarnating egos we have been in many bodies of flesh before, and the thoughts, feelings and actions generated in past lives have combined to lay the foundation for the type of body with its various characteristics that we inherit and use in this present life. The ideas we accept today as a basis for our thinking, feeling and action will in a future life be the foundation for the inner environment of thoughts and feelings that will mould a form through which these inner forces will find appropriate expression in the outer world of action.

Race, nation and family provide the necessary channels through which we acquire knowledge, by experience and observation, to accomplish the work for which we originally incarnated on earth. This work is the full acceptance of our responsibility as soul entities, and the discharging of all our daily duties from this viewpoint. It is because in our past lives our thoughts, feelings and actions affected other egos making up the race, nation and family to which we belonged that we are magnetically drawn to them again in this life, and they become our family and friends in the present and reap with us the effects of the causes sown. Under the Law of Karma, a law which balances the cause and the effect, outer circumstances and conditions are seen to be the effects and reflections of the collective thoughts, feelings and actions of all the egos making up the race, nation and family in which we reincarnate. Our intellectual, psychic and physical progress is, therefore, intimately connected with that of the collectivity of which we are a part.

The social conditions and environment we perceive around us are, from this point of view, partially of our own making, and so efforts at reform must be individual as well as collective. How this type of reform, culminating in true freedom on the intellectual, psychic and physical planes of being, can be achieved, may next be considered.

How can we think, feel and act in this present body so that our instruments may be attuned to the Great World-Soul, and in that attunement, find the power of knowledge to work intelligently with Nature's laws, and the capacity to help our brothers and sisters to accomplish a similar task? This question is clearly answered by Madame Blavatsky in The Key to Theosophy, where, in answer to the questions about Karma and Reincarnation and the individual's responsibilities to others, she says:

The individual cannot separate himself from the race, nor the race from the individual. The law of Karma applies equally to all although all are not equally developed. In helping on the development of others, the Theosophist believes that he is not only helping them to fulfil their Karma, but that he is also, in the strictest sense, fulfilling his own....If our present lives depend upon the development of certain principles which are a growth from the germs left by a previous existence, the law holds good as regards the future. Once grasp the idea that universal causation is not merely present, but past, present and future, and every action on our present plane falls naturally and easily into its true place, and is seen in its true relation to ourselves and to others. Every mean and selfish action sends us backward and not forward, while every noble thought and every unselfish deed are stepping-stones to the higher and more glorious planes of being.

These words are self-explanatory. Our task as individuals and Theosophists is simple: it is the acquisition, through study and application of the teachings of Theosophy, of the necessary knowledge by which we can promote true social co-operation and real efforts for social amelioration, with a view to the ultimate social emancipation of all such souls as are caught up in the web of Karma, helping them to understand and develop that sense of duty which a thorough understanding of the twin doctrines of Karma and Reincarnation alone can bring.

We have to go behind any idea of a Being, to the source of all being—to a basis common to the highest and to the lowest being. That basis and source is not to be found by looking outward at all, but is the very power to perceive, wherever there is life. Spirit, Life, Consciousness are the same in every being—undivided, however many and varied the perceptions. Evolution is not a compelling force from without, but the impelling force of Spirit from within, urging on to better and better expression. All advancement is from within. All the knowledge that we gain, all the experience that we obtain, is obtained and held within. Each one, then, is the Seer; all the rest are seen. So, the knowledge that we have to obtain is not information from without, not the thoughts of other men, but an understanding of our own essential nature, which represents every element in the great universe, from the basis of all life to every outward expression, and every possibility of further expression—just as each drop of water contains in itself everything existing in the great ocean from which it came. Nor does Law exist outside of us. Law is always inherent in Spirit; it is the action which brings reaction in every individual case, and to the collective mass of humanity. We are here under law and under justice. There is no such thing as injustice in the universe.

—Robert Crosbie