about his books and related subjects , such as abortion , Adolf Hitler , astrology , the appendix , blindness , blood transfusion , capital punishment , cause and effect , cremation , euthanasia , free will , homosexuality , karma , marriage , miscarriages , mongolism , overpopulation , psychopathy , space travel , suicide , the tonsils , transsexuality , Tutankhamun , UFOs , vegetarianism , vivisection and the Second World War .