"I had ascertained that in Bonaventure (as well as in theologians of the thirteenth century) there was nothing corresponding to our conception of 'revelation', by which we are normally in the habit of referring to all the revealed contents of the faith: it has even become a part of linguistic usage to refer to Sacred Scripture simply as 'revelation.' Such an identification would have been unthinkable in the language of the High Middle Ages. Here, 'revelation' is always a concept denoting an act. The word refers to the act in which God shows himself, not to the objectified result of this act. And because this is so, the receiving subject is always also a part of the concept of 'revelation.' Where there is no one to perceive 'revelation', no re-vel-ation has occurred, because no veil has been removed. By definition, revelation requires a someone who apprehends it. These insights, gained through my reading of Bonaventure, were later on very important for me at the time of the conciliar discussion on revelation, Scripture, and tradition. Because, if Bonaventure is right, then revelation precedes Scripture and becomes deposited in Scripture but is not simply identical with it. This in turn means that revelation is always something greater than what is merely written down. And this again means that there can be no such thing as pure sola scriptura ('by Scripture alone'), because an essential element of Scripture is the Church as understanding subject, and with this the fundamental sense of tradition already given."
-From his book Milestones: Memoirs 1927-1977.