The objection is specific and pointed. If there is one God who wants to communicate with humanity, and who has sent prophets across history to carry that communication, we would expect the messages to be broadly consistent — to converge on the same account of God’s nature, humanity’s situation, and the appropriate human response. Instead, we find substantial disagreement: on the nature of Jesus (divine son, prophet, or both?), on the structure of obligation (Sabbath observance, dietary laws), on the afterlife, on the relationship between this world and the divine.
Either the prophets were all authentic and God’s message is genuinely inconsistent — which is strange — or some of the claimed prophets were not authentic, or authentic messages were subsequently distorted beyond recovery. None of these options is obviously comfortable.
The Islamic account of prophetic history
The Islamic answer to this objection is built into its core account of revelation. It does not claim that every version of the Abrahamic message that currently exists is equally authentic. It claims that the original messages — the Torah given to Moses, the Injil (Gospel) given to Jesus — were genuine divine communications that were subsequently altered by human hands. The Quran is the final revelation that restores and preserves the original message in its uncorrupted form.
This is not special pleading invented to explain away competition. It is a coherent historical account that can be evaluated against the available evidence. The question of whether the Hebrew Bible and New Testament have been substantially altered from their original form is a legitimate historical question with a substantial body of scholarship bearing on it.
What the historical evidence shows
The textual history of the Hebrew Bible and New Testament is well-documented and shows development over time — editorial additions, theological redaction, adaptation for different communities, and in several well-documented cases the insertion of passages not present in the earliest manuscripts. The Johannine Comma (1 John 5:7-8) is a clear late addition to the New Testament in support of Trinitarian theology that does not appear in the earliest Greek manuscripts. The Pentateuch shows signs of multiple authorial and editorial hands.
This does not prove that these texts are not the word of God in any form. It does show that they have a compositional and transmission history that the Islamic account of textual corruption — tahrif — is at least consistent with.
The convergence beneath the divergence
It is also worth noting that beneath the theological divergence, the Abrahamic traditions share a striking core: one God, the creator of the universe, who is concerned with human moral life, who holds human beings accountable for their choices, and who is characterised by justice and mercy. The disagreements are substantial. The shared core is also substantial. The existence of that shared core is itself a datum: it suggests that the different traditions are drawing on a common original, however distorted the transmission.