An argument that atheists will bring up is the problem of incest in the early history of mankind, to prove that there is no God.
Genesis 5:4-5 “And the days of Adam after he had begotten Seth were eight hundred years: and he begat sons and daughters: And all the days that Adam lived were nine hundred and thirty years: and he died.”
Notice that Adam and Eve begat sons and daughters, after they gave birth to these children, they produced more children as well.
Genesis 5:6-7 “And Seth lived an hundred and five years, and begat Enos: And Seth lived after he begat Enos eight hundred and seven years, and begat sons and daughters:”
How in the world did Seth (Adam’s son) reproduce children, unless he married one of his siblings from Adam and Eve? Not only that, but from verses 8 to 32, many people filled out the whole earth, and the only way to do that was to marry a person in the family.
An irrelevant argument
Atheists are against God, they demand that no God exists. They use this example to prove their point. However, does incest in a family prove that there is no God? Of course not. This just means that God allowed incest to happen. This argument about incest in the family does not prove that there is no God. This is totally irrelevant.
Morals are relative
Next, we have to address why God allowed incest to happen back then in the Bible, in the prevalent culture of the Bible, but they would not argue about the culture of different nations? Atheists are all about relativity. They believe that morals are relative, that right and wrong depended on culture. Who are atheists to say that people marrying within the family then was wrong? They can’t argue that, because in the culture of that time, it was not regarded as wrong to do so.
Thousands of years ago, different nations had weird rules and strange practices, that to us today, we would think it to be wrong. The opposite is also true, that cultures back then would think that what we do today is also wrong. For example, Adam and Seth would look at us today and think that two males kissing each other are totally wrong!
Back then, there was only one man and one woman, and they had to repopulate the whole world. In their mind, it was common sense that they would have to interbreed with each other to do so. There was no other choice. But today, there are so many people around, and in this culture and environment, it is clearly wrong to marry one’s brother or sister.
Who dictates the laws of right and wrong?
A third point to ask the atheist, is who created the laws of right and wrong? It was the Lawgiver, who is God. It does not become wrong or evil until God says so. It is a matter of legitimacy, no matter who claims that it is unfair. Mankind is imperfect and sin every day, while God is perfect and infallible. A 100% holy God exists, who demands absolute perfection and holiness, who has the right to dictate what is wrong and right, because He knows past, present and future. It is impossible for God to sin. He is all-knowing, while mankind only knows partially. How can mankind question God’s methods of those days?
We human beings sin and therefore have no right to be able to determine what’s right and wrong.