Sexual abstinence or sexual restraint is the practice of refraining from some or all aspects of sexual activity for medical, psychological, legal, social, philosophical, moral, religious or other reasons. Sexual abstinence is distinct from asexuality, which is a sexual orientation where people do not feel sexual attraction. Celibacy is sexual abstinence generally motivated by factors such as an individual's personal or religious beliefs. Sexual abstinence before marriage is required in some societies by social norms, or by law in some countries. It is a part of chastity. Abstinence may be voluntary (when an individual chooses not to engage in sexual activity due to moral, religious, philosophical, or other reasons), an involuntary result of social circumstances (when one cannot find any willing sexual partners), or legally mandated (e.g. in countries where sexual activity outside marriage is illegal, in prisons etc.). History 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). Throughout history, and especially prior to the 20th century, there have been those who have held that sexual abstinence confers numerous health benefits. For males, lack of abstinence was thought to cause a reduction of vitality. In modern times, the argument has been phrased in biological terms, claiming that loss of semen through ejaculation results in a depletion of vital nutrients such as lecithin and phosphorus, which are also found at high levels in the brain. Conservation of the semen allegedly allows it to be reabsorbed back into the bloodstream and aid in the healthy development of the body. Along these lines, the noted German philosopher Friedrich Nietzsche spoke of the positive physiological effects of