One of the ways that make man attain knowledge is observation. Man is one of the witnesses and observers of the events in the universe. The universe is a book full of meanings that awaits to be read.

Many verses such as Behold what is in the heavens and the earth! (1),

Do they not look at the sky above them? How We have made it and adorned it, and there are no flaws in it? (2),

Look, then, to the signs of Gods mercy —how He restores life to the earth after its death... (3) call our attention to mans duty of observation. However, not everyone can make that observation. As indicated in the verse, there are many signs (things full of lessons) in the heavens and the earth people pass by and turn (their faces) away from them. (4)

Looking is different from seeing. Everyone looks at the universe but not everyone can see the secrets and the meanings in it. The verse You see them looking towards you, yet they do not see. (5) indicates the difference between looking and seeing.

The ones, who see the things that others cannot see, achieve the secrets of the book of the universe. For example, feeling that he got lighter in water, Archimedes found out the buoyant force of the water. Newton, receiving inspiration from the apple that fell on his head, realized the gravity force. Scientists, examining the structure of the wings of the birds, made human beings friends to birds by using the knowledge in aircraft industry.

If man gazes at the universe carefully, he can take an example and a lesson from everything. People, who have life in their hearts and contemplate the universe to discover a sign, can take a lesson from everything. Those who see everything as meaningless and go on their way in the darkness of unbelief are deprived of those wide and ample meanings. The Noble Quran uses the word blind for those people.

Those, who were blind in this world, will be blind in the Hereafter. (6)

Truly it is not their eyes that are blind, but their hearts which are in their breasts. (7)

But whosoever turns away from My message, verily for him is a life narrowed down, and we shall raise him up blind on the day Of Judgment. He will say O my Lord! Why hast thou raised me up blind, while I had sight (before)? Allah will say: Like this, Our Ayat (proofs, evidences, verses, lessons) came unto you, but you disregarded them; and so this Day, you will be neglected (in the Hell-fire, away from Allahs mercy). (8)

Vision (basar) is the seeing of the eye and insight (basirah) is the seeing of the heart. Those who do not have vision cannot see the things. Those who do not have insight cannot observe the essence of the things.

References:
1. Yunus, 101.
2. Qaf, 6.
3. Ar-Rum, 50.
4. Yusuf, 105.
5. Al-Araf, 198.
6. Al-Isra, 72.
7. Al-Hajj, 46.
8. Ta-ha, 124-126.