A midrash on Deut. 23:15 by Rabbi Pinhas ben Yair: "Care leads to cleanness, this to purity, this to holiness, this to humility, this to the fear of sin, this to piety, this to the holy spirit, this to the quickening of the dead, and this to Elijah the prophet."
This is fascinating, because it clearly states what I consider the contamination approach to spiritual life. Briefly this idea is that when the clean comes in contact with the unclean, the clean is contaminated.
The opposite view, and one which I would suggest is Jesus’ own with his recurring metaphors of light and salt, is what I call purification, which is the idea that when the clean comes in contact with the unclean it purifies it, removing its baser elements and cleanses it.
It seems to me that people fall roughly into either of these two camps as far as their spiritual life is concerned.
Myself, even though I prefer the Christian approach of purification, I must say that contamination certainly plays a part in spiritual life. But, no matter how infected a soul, it can always be purified and overthrown by the superior power of Love.