Discipleship is commitment to the King. Because the Messiah exists, he must be followed. An idea about the Messiah, a doctrinal system, a general religious recognition of grace or forgiveness of sins does not require discipleship. In truth, it even excludes discipleship; it is inimical to it.
One enters into a relationship with an idea by way of knowledge, enthusiasm, perhaps even by carrying it out, but never by personal obedient discipleship. Christianity without the living King, Jesus, remains necessarily a Christianity without discipleship; and a Christianity without discipleship is always a Christianity without King Jesus.
It is an idea, a myth.
A Christianity in which there is only God the Father, but not the King as a living Son, actually cancels discipleship. In that case there will be trust in God, but not discipleship.
(Dietrich Bonhoeffer, from Discipleship, p. 59)
Do you see!? It is so simple, but so sublime, and so helpful for one such as I who loves ideas. For, oh how I enjoy propositions, truths, doctrines, logical arguments, and dictums to be studied. Christianity has as part of it all these things. But if it were only these things, what would separate it from the other religious systems? For those systems can be entered into, as ideas, "by way of knowledge, enthusiasm, perhaps even by carrying it out, but never by personal obedient discipleship."
And that is the difference with Christianity. We have all these things, but we have so much more.
We have a living, real Jesus. An actual, breathing, enfleshed, and Divine King. And because he exists, as the true, living, real King, he must be followed. There is no neutrality when it comes to King Jesus.
Whoever is not with me is against me, and whoever does not gather with me scatters. (Luke 11:23, ESV)
Beloved, my fellow Christians, what a glorious truth above all other truths - Jesus is alive, and we are his disciples!