The first researcher in modern history to really get into the depths of the time we spend between lifetimes is Michael Newton. Thanks to the impressions of thousands of clients under hypnosis, he recorded the existence of 7 basic levels of spiritual growth. These were of course already known from other sources, like Hinduism and theosophy. This is growth in vibration. The weaker a soul is the lower its vibration, the stronger it is, the higher its vibration. As we act with unconditional love, forgiving ourselves and others, with modesty, bravery, selflessness and strength, we grow. If not, we remain stable and we’ll have to repeat the test.