When airplanes were first used in aerial warfare, it was relatively easy for antiaircraft units to recognize planes and identify them as allies or enemies. However, as speeds and altitude increased over the years, this became more and more difficult. During World War II it became imperative that defenders have assistance in identifying planes, and radar type equipment was developed to provide the needed information. It was called IFF equipment —Identification: Friend or Foe.
In wartime the necessity to identify planes is clear and urgent, but in day-to-day living it isn't always apparent that we need to identify ideas or thoughts that are presented to us. These can be either friends or foes, helpful or harmful. Those which cause us to hate, to be fearful, to resent, to be envious, are foes. These thoughts can result in pressures, anxiety, and illness. On the other hand, thoughts that cause us to want to be helpful to others, to be joyful, to be tender, kind, grateful, and loving are friends. They result in peace of mind, a feeling of well-being and goodwill, and they promote health.
Obviously we need some means, some radar-like sensitivity, with which we can detect quickly the quality of our thoughts and, most important, a method of purifying thought that will result in good in our experience as well as good for those around us.
