If a person develops good will it is certainly an excellent thing. However, just as the pendulum in its downward swing gathers the force that will make it swing upwards, so there develops with the force of good will a tendency to its opposite, a tendency to prejudice, biassed views and the like. No virtue can be cultivated without developing also a disposition towards the opposite vice. These truths are not comfortable but truths they are. In the individual they are less noticeable, but in public life they result in the kind of thing I have indicated. If people in one age one-sidedly cultivate some virtue and pride themselves over much in the fact, then people in the following age, although the connection is not recognized, will exhibit the corresponding vice.
Source: Rudolf Steiner – GA 176 – Karma of Materialism: Lecture 9 – Berlin, September 25, 1917