Evil is a construct which figures prominently in determinations of ethical behaviour as well as in emotional pathology and religious hysteria. Its definition is less important than its presence as a conception. Evil has been considered a side-product of many causes, coming not from one principle and having no unity in itself. When a body of any kind is infected with evil many of its elements do not keep their relative and just proportions; and to the extent that each part then strives to control the whole, disharmony prevails.
Evil, in one form or another, is a major concern of most religions. In 1993 the Pope published a new encyclical, Veritatis Splendor in which sex before marriage, contraception and homosexuality were labelled as intrinsically evil. In many cultures there is concern to guard against evil (including the "evil eye") and to avoid provoking evil spirits. The importance to the international community is reflected in a widely publicized perception by the President of the USA that the communist bloc of nations constituted an "evil empire".