For every light there is a shadow cast behind. It almost seems that light cannot but coexist with darkness. Does this mean we need darkness? That is debatable as well. The truth of the matter is that in the end, light and dark will completely separate.
The light of this world is goodness. The dark of this world is sin. Depending on how light is cast on a person, darkness will be seen differently. One person might view not accepting Jesus Christ as a sin. One might view praying as a good deed. But there is a light that always shines through even the darkest of shadows. In fact, it has no darkness. That is the light of Allah.
"Allah is the Light of the heavens and the earth. The example of His light is like a niche within which is a lamp, the lamp is within glass, the glass as if it were a pearly [white] star lit from [the oil of] a blessed olive tree, neither of the east nor of the west, whose oil would almost glow even if untouched by fire. Light upon light. Allah guides to His light whom He wills. And Allah presents examples for the people, and Allah is Knowing of all things." (Qu'ran 24:35)
Allah is perfect. And so is the religion of Islam. It is established to guide people into complete light and to deter shadows. When you follow its light, you won't fall into darkness. You will be freed from the darkness which the disbelievers experience. It is sheer hopelessness and lack of light. They are consumed by darkness.
"[they are] like darknesses within an unfathomable sea which is covered by waves, upon which are waves, over which are clouds - darknesses, some of them upon others. When one puts out his hand [therein], he can hardly see it. And he to whom Allah has not granted light - for him there is no light." (Qu'ran 24:40)
You fill find sin plunging you into a sea of darkness, while righteousness raises you into the lights of the celestial. For the disbeliever, he is swimming in the depths of a dark sea, lost, despairing. The believer on the other hand recognizes the darkness because he also has light. With his light, he casts away the shadows of doubt. He uses his good deeds to cast away sins. He is fighting an internal and external battle of light and dark. The light must always prevail, as a sign of its nature. The darkness will always dissipate into itself and collapse into itself, which is nothingness; similar to a black hole. There is so much darkness in a black hole that even light cannot escape. And that is the definition of the next life.
"Indeed, We have prepared for the disbelievers chains and shackles and a blaze." (Quran 76: 4)
There will never be any good in the Hellfire, and there will be complete evil 24/7. Conversely, the believers will be in complete light, rejoicing in the comfort of Paradise forever.
“They will not hear therein ill speech or commission of sin. But only the saying of: 'Peace! Peace!'" (Quran 56:25-26)
This is how dark and light will separate. There will be no more darkness for the believers, and there will be no more light for the disbelievers.
Thus is the battle between light and dark ongoing. But light will eventually win through.
"The believers must (eventually) win through,-" (Qu'ran 23:1)
Every person has their share of darkness. You must fight it with your light. Stay away from the darkness by abstaining from evil, and enlighten your heart by enjoining good. Then you will be among the successful in the next life.
Some things are light, and light is clear to see for the observer. It casts vision upon objects in our world. Some things are light, and are lack of light, and mislead you, leaving you in confusion and evil. Some things are twilight, uncertain of what is right and wrong, and it's best to avoid them.
“That which is lawful is clear and that which is unlawful is clear and between the two of them are doubtful [or ambiguous] matters about which not many people are knowledgeable. Thus, he who avoids these doubtful matters certainly clears himself in regard to his religion and his honor. But he who falls into the doubtful matters falls into that which is unlawful like the shepherd who pastures around a sanctuary, all but grazing therein. Verily every king has a sanctuary and Allah’s sanctuary is His prohibition. In the body there is a morsel of flesh which, if it be sound, all the body is sound and which, if it be diseased, all the body is diseased. This part of the body is the heart”. -Prophet Muhammad (SWS)
Look at the light that casts upon the objects before you to delight your vision. Look at the shades of darkness that lead to nothingness. What would you without your sight? Be grateful to the One who bestowed you that which discerns good from wrong, light from darkness.
"Then He proportioned him and breathed into him from His [created] soul and made for you hearing and vision and hearts; little are you grateful." (Qu'ran 32:9)