What was Salman Rushdie's purpose in writing Midnight's Children?

One purpose in writing Midnight's Children was to demonstrate the impossibility of a perfectly accurate retelling of history.  

When we normally think of "history," our mind drifts to an undisputed account. There is a belief that history has to be an objective and absolutely correct retelling of how factual events took place.  When we believe in this single notion of history, we tend to silence other voices or perceptions. Embracing this retelling of history...

One purpose in writing Midnight's Children was to demonstrate the impossibility of a perfectly accurate retelling of history.  

When we normally think of "history," our mind drifts to an undisputed account. There is a belief that history has to be an objective and absolutely correct retelling of how factual events took place.  When we believe in this single notion of history, we tend to silence other voices or perceptions. Embracing this retelling of history lends power to people who lay claim to the "truth" in the retelling of historical narratives.

One of Rushdie's purposes in writing Midnight's Children was to challenge this view of history.  Rushdie wants to address the history of modern India and Pakistan through the embrace of different stories.  There is no singular "authority" in Rushdie's version.  Saleem is the narrator, and claims to be infallible. However, he makes many errors in retelling the narrative of India, Pakistan, and the division that created both nations.  As a result, the view of history we get is not entirely accurate.  This underscores how any account that professes to be totalizing must be questioned.  

Through Saleem, Rushdie presents an imperfect account of history.  That is his purpose in writing Midnight's Children.   Rushdie believes that history is a collection of individuals, not infallible accounts:  "History is always ambiguous. Facts are hard to establish, and capable of being given many meanings. Reality is built on our prejudices, misconceptions and ignorance as well as on our perceptiveness and knowledge."  Rushdie wants to develop a history of India and of Partition that reflects the limitations intrinsic to human identity.   In doing so, his presentation of history in Midnight's Children causes the reader to wonder about what constitutes truth.