Shirk

The opposite of Tawhid is shirk: associating partners with Allah or worshipping something other than him. For example, treating a person or an object as a god would contradict the belief that Allah has no equal. Muslims consider shirk the gravest sin because it denies the central belief on which their worship rests.

Islam Q&A, for example, argues that people should address Allah directly: Allah is near, hears their prayers and needs no intermediary. It regards calling upon the dead for help or intercession as shirk, associating partners with Allah. This objection protects tawhid, the belief that Allah is one and alone deserves worship.