The division between the Orthodox and Roman Catholic Churches – officially almost a millennium old, but in many ways far older – has often enough been characterized as the ineluctable effect of one or another irreconcilable and irreducible difference: political (Caesars and Czars as opposed to princes and popes), cultural (Greek or Byzantine as opposed to Latin or Frankish), theological (divergent views of nature and grace or original sin), doctrinal (the filioque clause, papal infallibility, and so on), ritual (leavened bread and icons as opposed to azymes and statuary), ecclesiological (patriarchal pentarchy and sobornost as opposed to universal papal jurisdiction and monarchia), even ‘ontological’ – to cite the somewhat hermetic language once employed by the Oecumenical Patriarch. (I hope that this last was a case of mistranslation, I must note, as I should be inconsolable if I discovered that we do not even now have being in common.) And, because these various distinctions have been drawn only rarely in a spirit of critical detachment, uncontaminated by some element of squalid recrimination, it has usually proved difficult to separate matters of real significance from those raised for purposes either purely polemical or ultimately frivolous. Every serious ecumenical engagement between the Orthodox and Catholic communions reveals depth upon depth of substantial agreement, and yet always fades upon the midnight knell, as each side ruefully acknowledges the perplexing refractoriness and stubborn persistence of differences that lie (apparently) deeper still. Always an abiding sense of some ever more determinative – and yet, curiously, ever more indeterminate – essential difference overshadows every conversation (however charitable) that attempts to span the divide. And this sense serves constantly to temper our elation over whatever meagre accords we strike, to imbue our continued division with an almost mystical aura of inevitability, and to resign us fatalistically to our failures and to the failure of our love.