All praise is due to Allah, and may Allah's peace and blessings be upon His Messenger.
The basic principle regarding a person who has pronounced the two testimonies of faith (Shahadah), openly practices the symbols of Islam, fulfills its outward pillars, and was raised in a Muslim society is that they are treated as a Muslim in this worldly life. The outward rulings of Islam apply to them, and it is not permissible to declare them a disbeliever merely because they are unaware of the detailed matters of Tawhid or because they do not know the technical conditions of the statement "There is no deity worthy of worship except Allah." Worldly rulings are based on what is outwardly apparent, whereas what lies in the hearts is known only to Allah.
The Islamic texts clearly indicate that anyone who outwardly embraces Islam is granted the protection of life and property. This is established in the hadiths concerning the declaration of the Shahadah, the establishment of prayer, and the outward practice of Islamic rites. For this reason, the Prophet ﷺ forbade judging what is hidden in people's hearts. When Usamah ibn Zayd (may Allah be pleased with him) killed a man after he had pronounced the Shahadah, the Prophet ﷺ said:
"Did you open his heart?"
He also said:
"I have not been commanded to search into people's hearts."
However, being considered a Muslim outwardly does not necessarily mean that one has attained complete faith inwardly. The complete faith that benefits a person in the Hereafter requires understanding the meaning of the two testimonies of faith, believing in what they entail, and acting upon their implications by sincerely worshipping Allah alone, obeying His Messenger ﷺ, and submitting to His legislation. Merely pronouncing the Shahadah while turning away from its meaning and failing to act upon it does not benefit a person.
Nevertheless, this does not mean that every Muslim must memorize the technical wording of the conditions of "There is no deity worthy of worship except Allah" or know the scholarly classifications of those conditions. Rather, what is required is to realize their meanings in one's belief and actions. Thus, many ordinary Muslims may not be able to list these conditions, yet they truly believe in Allah and His Messenger, love them, obey the commands of Islam, and therefore fulfill the meanings of those conditions even if they do not know their technical names or scholarly details.
For this reason, the scholars of Ahl al-Sunnah have affirmed that ordinary Muslims who were born into Islam and adhere to its teachings possess the foundation of faith. Their faith increases in knowledge and certainty as they continue to learn and practice their religion. It is therefore impermissible to hastily declare them disbelievers because of ignorance regarding some of the finer details of Islamic creed, so long as they have not committed anything that nullifies the very foundation of Islam.
In summary, whoever pronounces the two testimonies of faith, establishes the outward practices of Islam, and grows up among Muslims is judged to be a Muslim outwardly. Their ignorance of the detailed conditions of the statement of Tawhid does not harm them, provided they believe in its meaning, submit to its implications, and strive to learn and practice their religion. As for the true reality of inward faith, its judgment belongs to Allah, the Most High.
And Allah knows best.