If that is really to come to pass which ought to come to pass, namely, that in the course of ensuing incarnations a sufficiently large number of people have a memory of this present incarnation, then provision for this must be made beforehand. Develop, therefore, your power of judgment; then you are candidates for the memory, in your next incarnation, of the present one. See to it that you are able to follow the world with your thoughts. For however much you can see in a visionary way, it will give you no help in remembering back to the present incarnation.
And it is the mission of Spiritual Science to prepare the way for what must needs come — namely, that there may be a sufficiently large number of people who out of their own knowledge can look back to this present incarnation. How many come to the point in this incarnation of accompanying their knowledge of Spiritual Science with clairvoyant powers depends on the karma of each individual.
There are certainly many sitting here whose karma will not allow them to see the world clairvoyantly in this incarnation. But all those who acquire what is given in true Spiritual Science, clothed as it is in the forms of thought, will reap the fruits of it in the next incarnation; for in this one they will have laid the right foundation.
Source: Rudolf Steiner – GA 117 – The Tasks and Aims of Spiritual Science – Stuttgart, November 13, 1909