I think that we need to seek such knowledge from a powrfull source such relegion. Here is a bit of this though lengthy a bit:
All the Prophets of God called their people to worship God and to believe in life after death. They laid so much emphasis on the belief in life after death that even a slight doubt in it meant denying God and made all other beliefs meaningless.
The very fact that all the Prophets of God have dealt with this metaphysical question of life after death so confidently and so uniformly - the gap between their ages in some cases, being thousands of years - goes to prove that the source of their knowledge of life after death as proclaimed by them all, was the same, i.e. Divine revelation.
We also know that these Prophets of God were greatly opposed by their people, mainly on the issue of life after death, as their people thought it impossible. But in spite of opposition, the Prophets won many sincere followers.
The question arises: what made those followers forsake the established beliefs, traditions and customs of their forefathers, notwithstanding the risk of being totally alienated from their own community? The simple answer is: they made use of their faculties of mind and heart and realized the truth.
Did they realize the truth through perceptual consciousness? They couldn’t, as perceptual experience of life after death is impossible. God has given man besides perceptual consciousness, rational, aesthetic and moral consciousness too. It is this consciousness that guides man regarding realities that cannot be verified through sensory data. That is why all the Prophets of God while calling people to believe in God and life after death, appeal to the aesthetic, moral and rational consciousness of man.
For example, when the idolaters of Makkah denied even the possibility of life after death, the Quran exposed the weakness of their stand by advancing very logical and rational arguments in support of it:
And he (i.e. man) presents for Us an example (i.e. attempting to establish the finality of death) and forgets his [own] creation. He says, “Who will give life to bones while they are disintegrated?” Say, “He will give them life who produced them the first time; and He is, of all creation, Knowing.” [It is] He who made for you from the green tree, fire, and then from it you ignite. Is not He who created the heavens and the earth Able to create the likes of them? Yes, [it is so]; and He is the Knowing Creator. (Quran, 36:78-81)
Surely God will raise all the dead. But God has His own plan of things. A day will come when the whole universe will be destroyed
and then the dead will be resurrected to stand before God. That day will be the beginning of a life that will never end, and on that day every person will be rewarded by God according to his or her good or evil deeds.
The explanation that the Quran gives about the necessity of life after death is what the moral consciousness of man demands. Actually, if there is no life after death, the very belief in God becomes meaningless or even if one believes in God, it would be n unjust and indifferent God, having once created man and now not being concerned with his fate.
Surely, God is just. He will punish the tyrants, whose crimes are beyond count - having tortured and killed hundreds or thousands of innocent people, created great corruption in society, enslaved numerous persons to serve their whims, etc., because man has a very short life span in this world and because numerous individuals are affected by one’s actions, adequate punishments and rewards are not possible in this life. The Quran very emphatically states that the Day of Judgment must come and that God will decide the fate of each soul according to his or her record of deeds:
But those who disbelieve say, “The Hour (i.e. the Day of Judgment) will not come to us.” Say, “Yes, by my Lord, it will surely come to you. [God is] the Knower of the unseen.” Not absent from Him is an atom’s weight within the heavens or within the earth or [what is] smaller than that or greater, except that it is in a clear register - That He may reward those who believe and do righteous deeds. Those will have forgiveness and noble provision. But those who strive against Our verses [seeking] to cause failure (i.e. to undermine their credibility) - for them will be a painful punishment of foul nature. (Quran, 34:3-5)
God states in the Quran about the events of the Day of Judgment:
Then when the Horn is blown with one blast, and the earth and the mountains are lifted and leveled with one blow [i.e. stroke] - Then on that Day, the Occurrence [i.e. Resurrection] will occur, And the heaven will split [open], for that Day it is infirm (i.e. weak, enfeebled and unstable). And the angels are at its edges. And there will bear the Throne of your Lord above them, that Day, eight [of them]. That Day, you will be exhibited [for judgment]; not hidden among you is anything concealed (i.e. any person or any secret you might attempt to conceal). So as for he who is given his record in his right hand, he will say, “Here, read my record! Indeed, I was certain that I would be meeting my account.” So he will be in a pleasant life - In an elevated Garden, Its [fruit] to be picked hanging near. [They will be told], “Eat and drink in satisfaction for what you put forth (i.e. literally, advanced in anticipation of reward in the Hereafter) in the days past.” But as for he who is given his record in his left hand, he will say, “Oh, I wish I had not been given my record, and had not known what is my account. I wish it [i.e. my death] had been the decisive one (i.e. ending life rather than being the gateway to eternal life). My wealth has not availed me. Gone from me is my authority.” [God will say], “Seize him and shackle him. Then into Hellfire drive him. Then into a chain whose length is seventy cubits insert him.” Indeed, he did not used to believe in God, the Most Great. (Quran, 69:13-33)
The Prophet Muhammad taught that three things continue to benefit a [believing] person even after death - charity which he had given (which continues to benefit others), beneficial knowledge which he had left behind (i.e. authored or taught), and supplication on his behalf by a righteous child (Narrated by Saheeh Muslim).
Thus, there are very convincing reasons to believe in life after death:
1) All the Prophets of God have called their people to believe in it.
2) Whenever a human society is built on the basis of this belief, it has been the most ideal and peaceful society, free of social and moral evils.
3) History bears witness that whenever this belief is rejected collectively by a group of people in spite of the repeated warning of the Prophet, the group as a whole has been punished by God even in this world.
4) Moral, aesthetic and rational faculties of man endorse the possibility of the life after death.
5) God’s attributes of Justice and Mercy have no meaning if there is no life after death.
A link to further reading:
http://www.islam-guide.com/life-after-death-by-wamy.htm
