One of the many books I read without quoting it in my STM thesis was “Bound to be free: Evangelical Catholic Engagements in Ecclesiology, ethics, and ecumensim” (2004) by Reinhard Hutter. This caught my attention:
The only way to think about the the church theologically that is neither sectarian, claiming the fragment as the whole, nor “Platonic,” forgoing the church’s concrete existence and settling for its bare idea, is specifically and forthrightly ecumenical. In short, ecclesiology – thinking theologically about the ekklésia – must be done ecumenically or it amounts to a self-deceptive sham that is bound to fail before it even begins. (p. 2)