How do Christians justify all of the inherent contradictions between the Old and New Testaments then? This is one thing I don't understand.
In the Old Testament, it is said:
"The person who sins will die. The son will not bear the punishment for the father's iniquity, nor will the father bear the punishment for the son's iniquity; the righteousness of the righteous will be upon himself, and the wickedness of the wicked will be upon himself" (Ezekiel 18:20).
This is completely consistent with Islam, but at complete odds with Christianity, which originated as an offshoot of Judaism. How can Christians adopt the concept of original sin when it is clear that people are responsible for their own sins.
Also, there are numerous references in the Old Testament about the Oneness of God, such as:
DEUTERONOMY 6:4 — Hear, O Israel: The LORD thy God is one LORD.
(Several more can be found
here.)
Furthermore, how did Jews and other people attain salvation before Jesus Christ? What about people who have never heard of the New Testament and Jesus, and died not knowing that they (according to you) were living a life of sin without having repented.
There are so many inconsistencies in the New Testament, and so much of the religion was voted on and constructed by people hundreds of years after the life of Jesus. Furthermore, unitarian Christian groups (like those in North Africa) were stamped out by the dominant Trinitarian Christian hierarchy. The same thing is true about countless other groups that interpreted the teachings of Jesus differently, and so many were declared heretical, forced to change their views or to die.