In the Quran, it is mentioned that the unbelievers are the people who does not recognize and appreciate the signs of Allah. The significance of a believer is his ability to see those signs and proofs. They know that these are not created in vain; they can realize the power and great art of Allah everywhere and find ways to appraise Him. About such people Allah Almighty Says (what means): "Who remember Allah while standing or sitting or [lying] on their sides and give thought to the creation of the heavens and the earth, [saying], 'Our Lord, You did not create this aimlessly; exalted are You [above such a thing]; then protect us from the punishment of the Fire.'"[Quran 3:191]
Many times in the Quran, there are expressions like "will you not take heed?", "...there is a sign for thinking men" which emphasize the importance of pondering on the signs of Allah. Allah has created an endless list of things to be the subjects of pondering. Everything we see and sense is indeed a manifestation and sign of Allah; so all those in heavens and in earth and in between may be a means of pondering for us. Allah Saya (what means): "He causes to grow for you thereby the crops, olives, palm trees, grapevines, and from all the fruits. Indeed in that is a sign for a people who give thought."[Quran 16: 11]
Let's think for a while of one of the items mentioned in the above verse; for instance, the "date-tree, as well known, grows up from a seed out of the earth. From this tiny seed (a seed is not even 1 cm3 in size), an enormous wooden mass of several meters long and hundreds of kilograms of weight, forms. The only thing that seed can use while constituting this great mass is the earth in which it is buried.
How can a seed know how to constitute a tree? How does it know how to decompose the necessary substances in the soil to form food? How can it predict the required shape and structure? This last question is especially important, because it is not an ordinary wooden piece that emerges out from the seed. The seed develops a complex living organism with roots for assimilating substances from the earth, with veins in itself and with branches that are perfectly organized. A human being has difficulty while drawing even a picture of a tree, but on the other hand a simple seed can produce that extremely complex object using the substances in the soil.
This observation concludes that a seed is extremely intelligent and wise, even more than us. Or better to say, there is an amazing intelligence in what a seed does. But what is the source of that intelligence? How can it be possible for a seed to have such an intelligence and memory like a computer "chip"?
The chips are produced by people who have intelligence and knowledge. Just like a seed which is created by Allah with the ability to develop a tree. Every seed on earth is encompassed by Allah and grows within His knowledge. He Almighty Says (what means): "Indeed, Allah is the cleaver of grain and date seeds. He brings the living out of the dead and brings the dead out of the living. That is Allah; so how are you deluded?"[Quran 6: 95]
A seed is merely one of the numerous signs that Allah has created in the universe. If men begin to think with not only their minds but also with their hearts, asking the question of 'why' and 'how' to themselves, they can understand that all the universe is a proof of the existence and power of Allah, the Most Exalted.
However, the unbelievers cannot understand such things, since they don't have the ability to "see" this purpose- as the Quran expresses (what means): "…They have eyes with which they do not see…"[Quran 7: 179] i.e., they do not have the wisdom and comprehension to realize the important reality with their materialistic vision.
On the other hand, believers are different than this 'blind' group, because they realize and accept that the whole universe is created by Allah with a certain aim and wisdom. This belief is the first step of faith. As faith and wisdom, both of which are in parallel, increase, they will start to identify every detail of Allah's creation.
One of the things to be done to identify the details of Allah's Creation is to be careful and observant. Because the ability to see the signs of Allah and not to be "blind" like the unbelievers, require a high concentration.
Allah Almighty Says (what means): "Unquestionably, to Allah belongs whatever is in the heavens and earth. Already He knows that upon which you [stand] and [knows] the Day when they will be returned to Him and He will inform them of what they have done. And Allah is Knowing of all things.."[Quran 24: 64]
"Unquestionably, they are in doubt about the meeting with their Lord. Unquestionably He is, of all things, encompassing." [Quran 41:54]
One should train himself to recognize the signs of Allah and should always keep this in mind. Otherwise, mind will start to wander, jumping from one topic to another, wasting time thinking about useless things.
Mind is like water; unless it is directed which way to flow, it spreads away, to the places that you would not want it to flow. This is a kind of unconsciousness; you cannot control your mind. You cannot focus and concentrate on a subject. Actually, you cannot conceive the truth behind the events happening and also cannot ever have the competence to interfere in them. On the contrary, your mind gets directed by those events. You are "bewildered" all the time, which is not an attribute of a believer, but the unbelievers, as Allah Almighty Says (what means): "...And he who associates with Allah – it is as though he had fallen from the sky and was snatched by the birds or the wind carried him down into a remote place."[Quran 22: 31]
Believers, on the other hand, are the ones who direct their minds, try to better perceive Allah, and who try to better serve His religion. The believers are the ones "who turn away from ill speech"[Quran 23:3]. They free their minds from any useless thoughts and whenever they realize the appeal of Satan, they rescue themselves just like Allah Almighty Says in the Quran (what means): "Indeed, those who fear Allah – when an impulse touches them from Satan, they remember [Him] and at once they have insight."[Quran 7: 201]
Therefore, the believers should be careful to keep their minds free of useless thoughts and ponder only on useful things that serve them in their life and keep them close to the Mighty Creator.
Tawheed (Islamic monotheism) is the greatest foundation of Islamic belief. In fact, a person is considered as Muslim if he/she accepts that there is no god worthy of worship but Allah and that Muhammad 
is His slave and His messenger to humankind.
Almighty Allah Says in the Noble Quran (what means): "Allah- there is no deity except Him, the Ever- Living, the Sustainer of [all] existence. Neither drowsiness overtakes Him nor sleep. To Him belongs whatever is in the heavens and whatever is on the earth. Who is it that can intercede with Him except by His permission? He knows what is [presently] before them and what will be after them, and they encompass not a thing of His knowledge except for what He wills. His Kursi (literally, a footstool) extends over the heavens and the earth, and their preservation tires Him not. And He is the Most High, the Most Great." [Quran 2: 255]
In these marvelous verses, Allah describes Himself as The Only One- Most Powerful, Ever-Living Lord of us. Tawheed is the bedrock of Islam and it states that it is Allah Who has created the universe with whatever is in it and administers it. What we deduce from the operation of the universe and call ‘natural laws’ are, in fact, Allah’s regular ways of creating things and events and administering the universe.
According to Islam, all religions revealed to the prophets, may Allah exalt their mention, have the same essence and knowledge of Tawheed and unity of Allah, but, with the time, the message was misinterpreted, mixed with superstition, and degenerated into magical practices and some rituals. That was the same message with which Adam, may Allah exalt his mention, was sent down to earth, the same knowledge that Allah revealed to Nooh (Noah), Ibraheem (Abraham), Moosa (Moses) and 'Eesa (Jesus), may Allah exalt their mention, and the last Prophet sent to humanity, Muhammad .
Islam rejects characterizing Allah in any human form or depicting Him as favoring certain individuals or nations on the basis of wealth, power, or race. However, our human minds are often in search of understanding the concept of Allah in materialistic ways, although we are not capable to completely comprehend this concept. When Prophet Muhammad’s contemporaries asked him about Allah and Allah revealed a chapter for this question in the Quran known as soorah Al-Ikhlas (Chapter No. 112 of Quran) which is considered as the motto of Tawheed. In this chapter Allah the Almighty Says (what means): "Say (O Muhammad), “He is Allah, [who is] One. Allah, the Eternal Refuge. He neither begets nor was He begotten. Nor is there to Him any equivalent." [Quran 112:1-4]
The Creator must be a different nature from the things created, because if He is of the same nature as they are, He will be temporal and will, therefore, need a maker. If the maker is not temporal, He must be eternal. But if He is eternal, He cannot be caused. If nothing apart from Him causes Him to continue to exist, He must be Self-Sufficient and Self-Subsistent. If He does not depend upon anything for the continuance of His own existence, this existence can have no end. The Creator is therefore Eternal and Everlasting Allah Says (what means): "He is the First and the Last" [Quran 57:3].
The Creator does not create only in the sense of bringing things into being, in other words, He is not only a Starter, He also preserves everything, takes them out of the existence, and is the ultimate cause of whatever happens to them.
'Ali Ibn Abu Talib 
the fourth Muslim Caliph, is reported to have said: "He is being but not through the phenomenon of coming into being. He exists but not from non-existence. He is with everything but not physical nearness. He is different from everything but not by physical separation. He acts but without the accompaniment of movements and instruments. He is the One, only such that there is none with whom He keeps company or whom He misses in his absence."
In Islam, Allah is known by His Names and Attributions and the manifestation of these names in the universe.
Another aspect of Tawheed in Islam is that it implies the equity and unity of all people in their relation with Allah. Thus, people of different social strata were not created by separate deities with varying levels of power, since this would violate Tawheed by putting barriers between them. Instead, social dimension of Tawheed states that the same Allah created everyone, and so all people have the same fundamental essence. In fact, the noblest person in Allah’s Sight is the one who is most Allah-conscious.
Prophet Muhammad said: “Your Lord is One. You are from Adam and Adam was created from dust. An Arab is not superior to a non-Arab, nor a white person over a black person, except for his/her piety and righteousness.” [Ahmad]
