This is where I have found the Eucharist section of the historic World Council of Churches document, Baptism, Eucharist, and Ministry (BEM) so helpful, because it lays out all the parts at once.  In the past I would share this with the deacons whenever we got into a muddle over what the Supper was all about, and I relied heavily on this material for my section on the sacraments in my A Course in Basic Christianity.

So, for example, these questions:

• Is the Lord’s Supper a thanksgiving to the Father?  Sure, that’s what eucharist means, and why the liturgy needs a Great Thanksgiving.
• Is the Lord’s Supper a memorial to the Son?  Of course, it is at least that, which is why the liturgy needs the Words of Institution.
• Is the Lord’s Supper an invocation of the Holy Spirit?  You bet!  Which is why the liturgy needs an epiclesis. (Notice the Trinitarian shape of these first three affirmations!)
• Is the Lord’s Supper a Communion of the faithful?  Yes,  there is the congregation embodying the church.
• Is the Lord’s Supper a meal of the kingdom?  Yes, it is a foretaste of the Great Heavenly Banquet, which is why several of our liturgies say, “This is the joyful feast of the people of God.”  (Notice the eschatology!)

In these five affirmations you have the Trinity, ecclesiology, and eschatology.  All of them need to be kept in view synoptically, or we go back to holding onto only one part of the elephant. Often it is not so much that we have been wrong in our affirmations about the Lord Supper, just unbalanced in emphasizing certain aspects and ignoring or neglecting others.

That is where ecumenism can be so helpful, when the mutual affirmation and admonition of fellow Christians enriches our understanding.