What is the Eucharist?

"Our aim in these few pages will be to explain what we believe takes place when we celebrate the Eucharist, what secret reality is made present for us in this rite as old as Christianity itself, the whole of whose mystery it bears within it. To explain means to bring to light all that can be brought to light concerning a truth whose origin is God himself. There will be two stages in this explanation. We shall first set out the actual terms of the doctrine which is of faith for all believers. We shall then try to acquire that type of understanding which is known as the intellectual grasp of the faith, or theology. This can never do away with the mystery. It reconciles reason to the mystery and even arouses its admiration for it and, at the same time, is pregnant with important consequences in the realm of daily life." [Introduction].