What is the definition of sound aqidah (creed), and is Imam Ibn Taymiyyah's definition the correct explanation that every Muslim should know, or is there another definition for Tawhid (monotheism)?

The meaning of sound doctrine (aqeedah) has been previously explained in prior fatwas. As for Ibn Taymiyyah's definition of aqeedah, he explicated the words of the righteous predecessors (Salaf As-Salih) and supported them with evidence from the Quran and Sunnah, and narrations from the first three centuries (of Islam). He mentioned that he diligently sought to follow the Quran and Sunnah in his aqeedah and negated distortion (tahrif). He did not mention the term "ta'wil" (interpretation/allegorical interpretation) due to its multiple meanings. He affirmed that his aqeedah conforms to the aqeedah of all the Salaf, and he challenged anyone who disagreed with him to produce a single letter from the first three centuries that contradicts it.