Is Halloween celebrated where you live? In the United States and Canada, Halloween is widely known and celebrated every year on October 31．Halloween customs, though, can be found in many other parts of the globe．In some places holidays are celebrated that, although named differently, share similar themes: contact with the spirit world involving the spirits of the dead, the devil and angels．Personally, you may not believe in supernatural spirits．You might simply view taking part in Halloween and similar celebrations as a way to have fun and teach your children to explore their imagination．Many people, though, regard these celebrations as harmful for the following reasons: Firstly,Halloween is actually related to the prospect of contact with spiritual forces, many of which threaten or frighten．Likewise, many celebrations like Halloween have religious origins and are deeply rooted in ancestor worship(祖先崇拜)．Even today, people around the world use these days to make contact with supposed spirits of the dead．Secondly, although Halloween has been viewed mainly as an American holiday, each year people in more and more countries have been adopting it．Many newcomers to the celebration, however, are unaware of the religious origins of Halloween symbols, decorations, and customs, most of which are related to supernatural beings and supernatural forces．Thirdly, thousands of people, who follow ancient Celts(凯尔特人), still call Halloween by the ancient name Samhain and consider it to be the most sacred night of the year．Others dont realize it, while theyre celebrating the Celtic holiday．In view of the foregoing, it is wise for you to know about the dark origins of Halloween and similar celebrations．Having this fuller understanding may help you decide whether to participate in these holidays.
According to the author, the theme of Halloween is to______.