A subject is controversial if two or more parties hold different opinions on its implications or solutions, especially in a public context. Parties' opinions on controversial subjects often differ due to conflicting ethical, social, religious, and political beliefs as well as their experience with particular issues.
Controversial subjects have existed throughout history. Some of the most widely debated controversies include alternative energy, the death penalty, immigration, religious freedom, sexual orientation and rights, gender equality, abortion, drug and alcohol uses and laws, and euthanasia. Controversial subjects also exist within different fields and categories. For example, some controversies in the fields of arts and education include banned books and censorship, cell phones and mobile devices, the value of education, the role of technology, and education reform.
Parties typically take positions on these issues based on what they believe is right in terms of ethics, morals, or practical solutions. It's important for someone who is considering which position to take to factor in his or her own value system, which sometimes depends on religious and political affiliations, as well as personal history and experience related to the issue. Conducting research on the Internet or at a local library is also a good way to find out what positions have already been established on various controversial subjects, which can help someone decide which side or solution best coincides with individual values and beliefs.