Christianity is not doing good things, helping the poor and sick, traditions, morality, philosophy, piety, social justice, or a religious experience. It's not about what people think it is, it's not what people have been doing for many many years. It's not just being good enough, being slightly better than the murderers and rapists out there. It's not a mindless following. It's not just something you fill in the blanks with. It's not something you can just get away with professing to be a Christian.
Christianity IS Jesus and what he did on the Cross for us. It is the Christ, the Messiah, the Saviour, finishing the work of atoning redemption as he hung there, suffered and died. It's the blood, the gore, the gruesome death, the shameful crucifixion. That blood shed for us, washed us clean. The death paid for us, releasing us from the bondage of sin. That crucifixion, meant for the worst criminals, was Jesus taking my place, where i the worst criminal belong. His life, the hope and promise of my redeemed life in the age to come.
And it also means we who are saved ought to live in a certain way:
It is gratefully submitting to the one True God, our whole lives as a living sacrifice. It is putting more importance on pleasing God rather than pleasing man. It's denying ourselves, denying our old sinful nature and clinging to the new creation we are in Christ. It is being committed to the gathering of the redeemed people, committed to the edification of the church. It is proclaiming the Gospel in everything you do, shouting it from the mountain tops or the lowest valleys.
It means we have to be reformed. And to never stop reforming. To cling to tradition is to make it more important than what the Word says, especially after it's lost its meaning. To always keep judging your life on the basis of what Christ demands of a disciple, lest you be judged on the last day and found wanting. It's finding glory and joy in the suffering, for it is only expected if you are a Christian. Anyone who follows Him, follows in the way he walked. In suffering and shame, in joyful obedience to the Lord, in being totally different from the current views and opinions of the time, in proclaiming the truth with power and authority, in rejection and harmful situations, even death. That's what it means to be Christian.