Understanding is always instantaneous, but each flash then needs a time to "settle" in the whole being. That is not instantaneous.
A good example was given by Krishnamurti with the case of getting rid of habits - it takes 3 days: one day to observe what happens to one, another day to others ... etc.
While the essentials are instantaneous sparks of observation, those sparks cause an effect on the entire system that takes time to manifest.
And the same happens globally; the people who mutated thanks to the teaching of K are few, its effect is discreet and it is not yet noticeable, but little by little humanity is being affected.
So we have that perception affects material level simultaneously instantaneously and gradually.
Part of a dialogue
