Sexual promiscuity is dangerous for many reasons. This is so because: (1) The aspirant's karma becomes entangled with the other person's. (2) One becomes psychically infected with low thought-forms hovering in the other person's aura. (3) Philosophy requires its adherents to consider the effects of their actions upon the lives and the character of others. We are to help their evolution, not their retrogression. (4) Intercourse with many unevolved types gives a special shock to the nervous systems of those who practise meditation and disintegrates something of their achievements each time.
-- Notebooks Category 5: The Body > Chapter 7: Sex > # 49