As for the Real Category (al-Qism al-Ḥaqīqī) of Islam, it has five essential requirements; it cannot be truly ascribed to a person if even one of these is missing:

The First: Submitting one's affairs to the Bearer of the Truthful Call from God the Exalted upon witnessing the miracle—which is the sign of truthfulness—with a heart sound and free from the diseases of doubt regarding any of his commands. Even if one is ignorant [of the wisdom], he accepts this incapacity regarding its meaning [trusting the source].

The Second: Faith in God, His Books, His Messengers, and His Angels, without slandering any of them or denying any of their spiritual stations.

The Third: Following all of their Outward Traditions (Sunan), and preserving everything God the Exalted has obligated through their tongues without neglecting anything, while desisting from all that they have forbidden.

The Fourth: Withholding the hand and the tongue from the blood, wealth, and honor of people, and avoiding their exposure.