OK, before we begin: a moment of sympathy for this wonderful Bible scholar having to live life with the name “Klyne Snodgrass“. Thank you.
Here’s what he says in his commentary on Ephesians:
We cannot be mature Christians by ourselves, for we cannot give ourselves everything we need for a life of faith. Christ could supply our needs directly, but instead He has chosen to grace other people so that they contribute to us and we to them. Grace comes from God but it is also conveyed through horizontal channels. Or, as F.F. Bruce puts it, “The higher reaches of the Christian life cannot be attained in isolation from one’s fellow believers.”
This is why we must have the church.