The next stage, the purification of the spirit, is the first stage for those who are called the proficients.
The early stages of the proficients only come after the completion of the purification of the senses. Here are the elements which would indicate that one is in the start of the purification of the spirit.
Why does the spirit need purifying. by the way? Because all the evils of one's characters lie in the spirit. But, it is only after the purification of the senses that this purification can begin.
One cannot skip stages, and those who teach that this is possible are ignoring the wisdom of centuries of holy men and women who have shared their experiences with the Church.
One learns fortitude in the Dark Night of the Senses, which is absolutely necessary for the enduring of the Dark Night of the Spirit.
Here are some elements of this second part of the Dark Night taken from St. John of the Cross.
1) The time of darkness means that the intellect, memory, understanding and will are all in a shadow. One does not see the way and must rely on Divine Providence entirely.
2) One begins to finally do great works for God Alone and not for one's ego. In this darkness, one can and should work for God, with a new power which comes from the lack of reliance on the senses.
3) One is inspired by Divine Wisdom and not by one's own studies or knowledge. God places ideas in the intellect, as inspirations.
4) A person's will is inspired by God as well. This means that God is directing the will, which has been entirely turned over to God.
5) Few people persist in this state, as it is painful. Although all men and woman are called to this state, few persist in the darkness which is demanded of pure trust in God.
8) A new purification of the spirit happens, which is not understood by those who experience this. God is allowing one to experience His Love in a new manner, which leads to infused contemplation.
9) If persons do not experience this state or the one previous to this, one must endure purgatory. And, part of the pain of purgatory is understanding that one could have followed this path on earth for the good of one's soul and the good of the Church, but refused to do so.
10) Therefore, a generosity of spirit must accompany this state. The intellect, memory, understanding, will are all directed by God directly and not by the person.
11) This is still not the Unitive State, but is the last stage before the Illuminative State. The Illuminative State only occurs after the spirit has been purified.