Apostatise is a verb that means to renounce a religious or political belief or principle. It is also spelled as apostatize in American English. People who apostatise are called apostates, and the act of apostatising is called apostasy.

There are many reasons why people may choose to apostatise from their religion or ideology. Some of the common ones are:

• Personal experience: Some people may have negative or traumatic experiences that make them question or reject their faith or cause. For example, they may suffer from abuse, discrimination, violence, or persecution because of their beliefs, or they may witness or learn about atrocities committed by their co-religionists or fellow members.
• Intellectual inquiry: Some people may have doubts or disagreements with the doctrines, teachings, or practices of their religion or ideology. They may find them illogical, inconsistent, contradictory, outdated, or immoral. They may also be exposed to alternative views or evidence that challenge their beliefs or persuade them to adopt a different perspective.
• Social influence: Some people may be influenced by their family, friends, peers, mentors, role models, or media to change their beliefs or affiliations. They may feel pressure, coercion, temptation, or attraction to conform to the norms or expectations of their social group. They may also seek acceptance, approval, belonging, or love from others who have different beliefs or values.

Apostasy is often considered a serious offense or betrayal by those who remain faithful to their religion or ideology. Apostates may face ostracism, condemnation, harassment, threats, violence, or even death from their former community. However, apostates may also find freedom, happiness, peace, fulfillment, or enlightenment in their new beliefs or identity. Apostasy is a complex and personal phenomenon that reflects the diversity and dynamism of human thought and experience.

Apostasy has occurred throughout history and across cultures. Some of the famous or notorious examples of apostasy are:

• Martin Luther: He was a German monk and theologian who initiated the Protestant Reformation in the 16th century. He challenged the authority and doctrines of the Roman Catholic Church and was excommunicated by the Pope. He is regarded as a hero by many Protestants and a heretic by many Catholics.
• Salman Rushdie: He is a British-Indian novelist and essayist who wrote The Satanic Verses in 1988. The book was considered blasphemous by many Muslims and provoked a fatwa (a religious edict) by the Iranian leader Ayatollah Khomeini, calling for his death. He has lived under police protection and in hiding ever since.
• Meghan Markle: She is an American actress and humanitarian who married Prince Harry of the British royal family in 2018. She renounced her American citizenship and became a member of the Church of England as part of her marriage. However, in 2020, she and her husband announced their decision to step back from their royal duties and move to North America.

Apostasy can have various consequences for the apostates and their former and new communities. Some of the possible consequences are:

• Psychological effects: Apostates may experience guilt, shame, fear, anger, sadness, or relief as they cope with their change of beliefs or identity. They may also face cognitive dissonance, identity crisis, or existential questions as they try to reconcile their past and present selves.
• Social effects: Apostates may lose their social support, network, or status as they sever ties with their former community. They may also face discrimination, stigma, or hostility from their former or new community. They may have to rebuild their relationships, trust, or reputation with others who share or respect their new beliefs or values.
• Legal effects: Apostates may face legal challenges or risks as they change their citizenship, nationality, or affiliation. They may also face legal persecution or prosecution from their former or new community. They may have to seek asylum, protection, or justice from authorities or organizations that uphold their human rights and freedoms.