Religion

by adults that the children love and trust is extremely effective and difficult to overcome. That's why religion is usually drilled into children before they're even old enough to understand what it is they're being taught. Combine that with negative consequences, often including the threat of eternal torture, for expressing incredulity, or asking the "wrong" kind of questions. Now you have an adult who's been thoroughly conditioned to accept these ideas, and to experience real fear if they ever begin to doubt that they're true.