What kind of knowing allows us to really know things as they are, and yet also allows things to be mysterious?
This is what Balthasar wrestles with and claims it is possible to "arrive at an intelligibility" (an understanding) that illuminates the pure facticity of the historical necessity, and at the same time an intelligibility (understanding) that cannot be reduced to that which the human being demands or (for whatever reason) anticipates. In other words, it is possible for an understanding to exist that uses the facts of history to express itself, while at the same time expressing something that cannot be explained or predicted using only facts ("Cannot be reduced to what the human being deamnds...or anticipates".)
The branch of philosophy called “epistemology” deals with ways of knowing, and examines what we can mean by “knowing”. The most popular example is how we “know” the truths and wisdoms of the Bible’s New Testament by interpreting the prophecies of the Old Testament. This example may also serve as an example of Balthazar’s contention that we can use history to express truth without explaining truth. A more mundane example might be using the Bill of Rights to express what we mean by the truth that “all men are created equal,” without really explaining what the human means” by “equal.” It is often pointed out that humans are not created equal in health, size, intelligence, etc. So what is meant? In epistemology there are a myriad of avenues to “knowing.” A recent example is the advertisement for a luxury automobile that implies that owning/driving that brand lets others “know” something about the owner’s taste, refinement, financial status, etc. Many millions “know” that God is Good, and that He/She is watching over us (“His eye is on the sparrow”) without diminishing the “mystery” of His/Her being. We can scientifically “understand” the Food Chain and DNA, and still be intrigued by the Darwinian history of Life on earth. This is the essence of Balthazar’s stance on epistemology.