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.
Allah Almighty said:
{No vision can encompass Him, but He encompasses all vision, and He is the Most Subtle, the All-Aware.} [22] Surat al-An‘ām: 103.
As an example to make things clear only, man cannot describe something immaterial like the "idea". He cannot identify its weight in grams, its length in centimeters, its chemical structure, its color, its pressure, its form, and its image.
Perception is classified into four types, which are:
Sensual perception: like seeing an object by using the sight.
Imaginary perception: like comparing a physical image with something in one's memory and in one's previous experiences.
Illusory perception: which is feeling how others feel, like someone feeling that his son is sad.
These three types are common between mankind and animals.
Mental perception, which is the kind of perception that is unique to man.
Atheists want to omit this kind of perception to put man on the same level with animals. Mental perception is the strongest kind of perception because the mind is what rectifies the sense. For instance, when one sees a mirage, as mentioned in the previous example, it is the mind's job to tell him that this is just an illusion and not water and it appears only because of the reflection of light on sand and it does not really exist. So, here one is deluded by his sense and guided by his mind. Atheists reject the mental evidence and demand a material evidence, which they refer to as "scientific evidence". Is the mental and logical evidence not scientific as well? As a matter of fact, it is scientific evidence; however, it is not material evidence. Try to imagine the reaction of someone who lived on planet earth five hundred years ago to the mere idea of the existence of minute microbes that could not be seen with the bare eyes. [23] Fadel Soliman https://www.youtube.com/watch?v=P3InWgcv18A
Despite the fact that the mind can perceive the Creator's existence and some of His attributes; nevertheless, it has boundaries. It can perceive the wisdom behind some issues and fail to perceive it in other issues. No one, for example, can perceive the wisdom in the mind of a physicist like Einstein.
"Bear in mind that Allah has the highest attributes, and the mere assumption that one has the ability to encompass the complete perception of Allah proves nothing but one's ignorance about Him. Your car may take you to the beach but cannot take you inside the sea. If I ask you, for instance, about the sea water and how many liters it contains and you answered by giving any number, in this case you are ignorant. However, if you reply by saying that you do not know, then this indicates your knowledge. The only way to know Allah is through His signs in the universe and through His Qur’anic verses." [24] From the sayings of Shaykh Muhammad Rātib an-Nābulsi.
The sources of knowledge in Islam are: the Qur’an, the Sunnah, the consensus, and what is proven by the sound mind, which is subservient to the Qur’an and Sunnah, that does not contradict the revelation. Allah has made the mind to find guidance in the universal signs and the material issues that confirm the facts mentioned in the revelation and do not contradict it.
Allah Almighty said:
{Do they not see how Allah originates the creation then resurrects it? That is certainly easy for Allah. Say, “Travel through the land and see how He originated the creation, then Allah will repeat it a second time. Indeed, Allah is Most Capable of all things.”} [25] Surat al-‘Ankabūt: 19-20.
{Then he revealed to His slave what he had to reveal.} [26] Surat an-Najm: 10.
The most beautiful thing about knowledge is that it is limitless, and the more we delve in sciences the more sciences we shall discover and we will never be able to encompass all knowledge. The smartest person is the one who tries to understand everything, but the most stupid person is the one who thinks he can understand everything.
Allah Almighty said:
{Say, “If the ocean were ink for [writing] the Words of my Lord, the ocean would surely run dry before the Words of my Lord are finished, even if We brought its like to resupply it.”} [27] Surat al-Kahf: 109.