That depends on who is defining Christianity. Basic Christianity is the understanding that a person cannot do anything, including good works or good deeds, to win a place in heaven. Christianity alone teaches that forgiveness of individual sin and the promise of eternal life with God are gifts offered to an individual by God. To receive these gifts of both forgiveness and eternal life, one only has to accept the gift by faith in Jesus Christ as Lord and Savior. So the question becomes, is Jesus true? Is what he says about himself truthful?
Jesus, the first-century teacher, is documented in the Bible and by historians of that period, Josephus and Tacitus. His teachings are among the best-preserved words from antiquity. His birth, life, teachings, miracles, death and resurrection were all prophesied more than 500 years before he was born. Only God, who exists beyond both time and space, could know the future.
Jesus’ miracles demonstrated his divine power. In his three and a half years of ministry, thousands were healed of all sorts of diseases and these events had many witnesses to testify to their authenticity. His death and resurrection are documented historical facts. After he rose from the dead Jesus was seen by more than 500 people, over a span of 40 days. Jesus’ ascension back into heaven had many witnesses proving again he was the Son of God. In addition, there are thousands of verified reports of Jesus appearing to people throughout the world, even to Muslims, who are accepting in great numbers the truth of Jesus as the human manifestation of God. They are recognizing that Jesus is the only path to an eternal relationship with God, the creator of the universe–the only entity who can bring true peace to the human soul and to the world.
Throughout history, many people have tried to hijack Christianity, to use the religion to advance their personal agendas. They have distorted the teachings of Jesus. They have killed and bullied and destroyed in the name of Jesus. However, even a casual reading of the Bible clearly demonstrates that Christians are called to love their enemies, to serve the poor, care for widows and orphans, and to reflect the love of Jesus in all they do. They are called into a life of service on behalf of God, not because God demands it, but because they are so thankful for what he has already done for them. This is the truth of Christianity. By contrast, all other religious systems are either unverifiable or irrational, thereby disqualifying them as being true. For these reasons alone you can know for certain that Christianity is true, but the question is, Do you believe it?
Every individual has the free will to receive God’s gift of salvation or reject it and pursue their own self-centered life. Heaven and Hell hang in the balance of this decision. All other religions propose a path to God. Unfortunately, the fact is these are all dead ends leading to eternal destruction. There is no path. There is only the Way of Jesus Christ because he is the Truth and he is God. (John 14:6)