Although we could see the rainbow and the mirage, yet they do not actually exist. Moreover, we believe in the existence of gravity without seeing it just because its existence was proven by the material science.
{Indeed, Allah commands you to return trusts to their owners, and when you judge between people, judge with justice. What an excellent exhortation from Allah to you! Indeed, Allah is All-Hearing, All-Seeing.} [234] Surat an-Nisā’: 58.