Perhaps the oldest and strongest objection to the Christian faith is what C. S. Lewis has called the problem of pain. Today, however, I believe the most common objection to Christianity is what I will call the problem of pluralism.
The problem of pluralism springs from the following simple observation. All around the world, from Italy to India, science textbooks say the same thing. No matter the location, virtually every educated person agrees that f=ma or e=mc^2. With religion, however, there is virtually no consensus. People in Calcutta are Hindus; people in Rome are Catholics.
This observation produces in many a certain intuition that the exclusive claims of Christianity simply cannot be true. Nevertheless, this observation alone cannot furnish any convincing argument against the Christian faith. Obviously, lack of consensus does not prove a proposition false. For example, there was a point in time in which only one man on the planet believed that e=mc^2, but he was nevertheless correct. Likewise, the presence of consensus does not prove a proposition true. For example, there was a time when nearly everyone believed that the Sun orbited the Earth, but they were all wrong.
However, one may protest that the claims of science eventually enjoy consensus, while the claims of religion never do. This is, of course, because the claims of science are empirically verifiable in a way that the claims of religion are not. Nevertheless, the fact that the claims of religion cannot be empirically verified is hardly proof that Christianity is false. For example, modern scientists cannot empirically verify that Caesar crossed the Rubicon, but this is no reason to doubt the ancient historians.
At this point, one might protest that there is nevertheless universal consensus that Caesar crossed the Rubicon. There is no such consensus, however, that Jesus rose from the dead. Surely this lack of consensus demonstrates that religion, unlike history and science, does not deal in objective fact. However, the historical proposition of Christ’s resurrection is more controversial than the historical proposition of Caesar’s crossing only because the former conflicts with certain religious or metaphysical beliefs. None of those beliefs, however, enjoys any more consensus than Christianity!
So in conclusion, the problem of pluralism is not really a problem at all. It is more akin to the discomfort you feel when you complete a complicated math problem, only to discover that many of your classmates got a different answer. This is certainly a disquieting feeling, and it should prompt you to double check your work. However, it hardly causes you to stop believing in arithmetic.