The ancient world discouraged promiscuity for both health and social reasons. According to Pythagoras (6th century BCE) sex should be practiced in the winter, but not the summer, but was harmful to male health in every season because the loss of semen was dangerous, hard to control and both physically and spiritually exhausting, but had no effect on females. This idea may have been merged with Zoroastrian ideas of good and evil in a philosophy known as Gnosticism, which influenced Christian and Islamic attitudes to sexual activity. But others stated that the Christian religion's hold on to the ideal of sexual abstinence prior to the appearing of gnosticism and Zoroastrianism and its roots are to be found in the Old Testament (which is the base of the New Testament) in which virginity was required by law and marriage was especially protected (see Deuteronomy chapter 22).