Belief in the unseen is the first component of belief. There are three types of the unseen:

• That which is hidden from you but there are ways of finding out about them, such as meteorology which can inform us of the weather. This is not considered among the unseen.
• That which is hidden from you but is known to others. This is not considered as the unseen.
• That which is absolutely hidden and there are no means of finding out about them.

For example, there are some people who deny the existence of jinn because they are unable to see them. Why then do they not deny the existence of germs?

The jinns do not have knowledge of the unseen. If they claim that they do, it is actually a thing which exists in another part of the Earth that they have access to. Allah U has says:

﴾فَلَمَّا خَرَّ تَبَيَّنَتْ الْجِنُّ أَنْ لَوْ كَانُوا يَعْلَمُونَ الْغَيْبَ مَا لَبِثُوا فِي الْعَذَابِ الْمُهِينِ ﴿

“But when he fell, it became clear to the jinn that if they had known the unseen, they would not have remained in humiliating punishment.”        [Surah Saba’: 14].

From here, it is clear that they do not know the unseen. Similarly, the angels do not have knowledge of the unseen. The proof is the verse:
 ﴾قَالُوا سُبْحَانَكَ لا عِلْمَ لَنَا إِلاَّ مَا عَلَّمْتَنَا إِنَّكَ أَنْتَ الْعَلِيمُ الْحَكِيمُ﴿

“They said, “Exalted are You; we have no knowledge except what You have taught us. Indeed, it is You who is the Knowing, the Wise.”  [Surah Al-Baqarah: 32].