The case for Christianity and Mere Christianity, while related, are not exactly the same. Mere Christianity is a book by C.S. Lewis that seeks to distill the essential beliefs of Christianity down to their core, presenting a common ground shared by different denominations.
On the other hand, the case for Christianity can refer more broadly to the arguments and evidence that support the truth of Christianity as a whole. This includes historical, philosophical, and theological aspects that affirm the faith’s claims.
To clarify, Mere Christianity focuses on what all Christians can agree upon – the basics of the faith that go beyond doctrinal differences. In contrast, making a case for Christianity might involve deeper theological debates and discussions that go beyond those basics, addressing not only core beliefs but also specific doctrines unique to certain denominations or interpretations.
In essence, while Mere Christianity provides a foundation for understanding Christianity at its simplest level, the broader case for Christianity can delve into more complex discussions about its validity and implications in the modern world.