Is ignorance a matter of legitimate difference of opinion, or is the correct view that there is no excuse for ignorance and that whoever differs is an innovator? And what are the evidences of each group?

Ignorance as an excuse varies depending on the issues and individuals. In certain matters, such as belief in divine decree, the obligation of prayer and zakat, and the prohibition of injustice and lying, ignorance is not excused except for someone who is new to Islam or grew up in a remote desert.

Shaykh al-Islam Ibn Taymiyyah stated that takfir (declaring someone an unbeliever) is a form of warning, and a denier might not be declared an unbeliever until proof is established against him. He gave the example of the man who asked for his body to be burned and scattered in the sea out of fear of Allah. Allah forgave him for his ignorance despite the disbelief in his conviction.

Ibn Taymiyyah added that denying the four fundamental obligations or apparent prohibitions after proof has been established constitutes disbelief.

Al-Suyuti mentioned that whoever is ignorant of the prohibition of something commonly known by most people, their claim of ignorance is not accepted, except for someone new to Islam or one who grew up in a remote desert, such as the prohibition of adultery, murder, theft, and alcohol.

This summary clarifies the criteria for issues in which ignorance is not excused and those in which it is.