Joining a church informally: demonstrates a desire to belong to a particular congregation; perhaps as a confirming sign of personal satisfaction, and happiness, arising out of sharing in something of that church's life.
However, joining a church, informally, is not the same thing as entering the church, in a recognized and formal manner. To say this, is not merely to fiddle about with the meaning of words
For centuries; the Church has held the belief, that joining; in the manner just touched on; is not enough: for the Church is not a club – but a way of life.
Entering goes far beyond joining, at three levels. Firstly, it demonstrates a desire, not merely to be associated with, but to be an integral part of that particular congregation: and to have a commitment to its way of life.
Secondly, entering recognizes the historical past, and present importance, of the Church, at the national level: and claims a part, in that wider life.
Thirdly, entering acknowledges that Christ instituted and commissioned his Church on the worldwide scale: and recognizes that each member of a local congregation; not only belongs there; but also has place, and purpose, in the Lord’s greater scheme of things.
When Jesus Christ came into the world; as Messiah and Redeemer; he did not join humanity, by merely coming alongside it, on the same planet. Instead, he entered into humanity; and became a part of it, of the same flesh.
We may think that, coming alongside the Church, through joining it; brings rewards and blessings. Maybe so: but it is only by entering it, and being an integral part of it, that the best that the Church represents and offers, can become part of us.
When Christ commissioned his Church, he called it to a unity of faith and purpose: designed to lead to a unity of mind and spirit; that, eventually, leads to unity with God’s holy purposes of love and redemption.
To believe that the Church is a God-appointed channel: within which a spirit of togetherness and belonging prevails; and through which teaching; witness and outreach are undertaken; is good; but by no means enough: for we also belong in the other and greater sense, that St. Paul taught, in his various letters.  He wrote of each committed Christian being a 'member' of the 'Body of Christ'.
A concept can become fixed in our minds: stifling the impetus necessary to moving on, towards the reality to which the concept points. This can be true of the Church. Some people seem to feel that just being there is enough.
However: going to Italy does not, of itself, make us Italian: and living near a college in Oxford, does not, of itself, make us a Master of Arts: and our physical presence, in a church, does not, of itself, make us an actual member.
Concepts requiring practical application to fulfil them: must be translated into events, where certain actions and words, are undertaken, and spoken. And so it is with entry into the Church.
Baptism; is the first, and essential, step, into true belonging. In this: we follow the example of Christ’s baptism, in the River Jordan. We speak of being baptized into the Church or into Christ; but into what was he baptized?  Not into the Church, for it did not exist at that time: not into himself, for that would have been illogical.
Jesus was baptized into frail, sinful humanity.
John the Baptist offered 'baptism for the forgiveness of sins’. Jesus insisted that he, too, had to undergo that exact, same baptism: or else what was required of him could not be fulfilled – so he and John got on with it.
Up to that moment: by some holy mystery, Jesus was fully God, and fully man. As John pushed him down under the water, a radical change took place.
Jesus was emptied of his Godly qualities; and all the gaps left, were filled with the frailty of sinful mankind. When he came up out of the water, spluttering and blowing, he had, indeed, entered into humanity.
He was of the same flesh; and imbued with the same human needs, hopes, and fears as all the rest of mankind.
Standing there: was a man who, of himself, could not undertake the ministry that was opening up before him. Of himself: he could not be the teacher and leader that he was called to become; let alone Messiah and Saviour.
Something had to be done! By the Hand of God: it was done!
The Holy Spirit came upon Jesus; entered his frail, human body; and endued him with spiritual discernment as to what was needful; and with spiritual power to undertake what was necessary.
From that moment on, he became the Christ, to the world.
As said: at his baptism, Jesus became so much like us; that something had to be done; to enable him to fulfil his calling. Through the infilling of the Holy Spirit; all that was needful, was done.
Although, in baptisms within our churches, we claim that we are baptized into Christ:  we do not, immediately, become Christ-like. No matter how we may try to empty ourselves of human frailty: and to fill ourselves with Godly qualities; we will never succeed, on our own. Something else is needed; and only God can provide what is needful.
At his baptism, Christ demonstrated his full commitment to needy humanity: something that he could not undertake, without the Holy Spirit’s help.
It is the same with us. The Church’s ‘entry’ events, express our desire to be fully committed to Christ: but the words that we use, recognize that we cannot do this, without the Holy Spirit’s continual help.
The Church (with a capital ‘C’) recognizes that baptism is an early-on ‘milestone’, along the road of ongoing faith: that there is a long way yet to go; and that the way ahead, is through an earnest desire to enter, more fully, into the new life that God gives, in Christ.
The Church (still with a capital ‘C’) recognizes that the next, and essential, ‘milestone’: is that those undertaking the spiritual journey; must accept Jesus Christ as their personal God, Saviour and Lord…
…for only then can they receive the desired new life; and become, no matter how gradually, more Christ-like, in mind and spirit.
Lastly, for present purposes, the Church (still with a capital ‘C’) teaches the importance of that further, and very personal event: known as a ‘Membership service’, or, more commonly, ‘Confirmation’.
At its best: the event encourages those seeking formal entry into the Church; to confirm their commitment to all that true, Christian belonging entails.
Commitment to Christ himself: lead where it will. Practical commitment to the local church: and commitment to the higher vision, of the worldwide Church. More importantly, spiritual commitment to the Church’s calling, as the mystical ‘Body of Christ’.
All this, and more, has been known for centuries: but what do individual churches (with a lower-case ‘c’) actually do about it.
Many behave as though new people joining the congregation: is enough. Those churches failing to nurture and teach such people: doing nothing to encourage them to enter into the Church, through accepting all that such entry entails – also fail to obey Christ’s call, and commission.
Local churches, including ours, must never see themselves as being in their own small corner: mere, unimportant extensions of ‘The Church’ which, somehow, belongs elsewhere.
Instead: for all of the practical and spiritual purposes, that God’s calling lays upon it; each local congregation is ‘The Body of Christ on Earth’, to itself; and to those all around it.
If we believe this to be so: are we actually fulfilling our calling? Do we nurture and teach new people who join; thus encouraging and enabling them to enter into that part of the ‘Holy Church of God’; that lies within our care?