Logical positivism was an early 20th century branch of philosophy, so there's been about a century of philosophical musing on it. In simple terms, it assumes that the world, and our thoughts about it, consist of elementary facts and that we can apply logical rules to these facts to establish the truth. However, probably the most famous phrase is translated as something like: on that we cannot speak we must remain silent. This is sometimes interpreted as ambivalence in logical positivism towards nonsense, mysticism, gods and so on. It doesn't outright deny their existence but says that philosophers can't say anything about them because they're inherently outside of logical analysis.
I guess that's what faith is: Belief in things which are outside of logical analysis, which (as the author put it, a bit oddly) "Cannot be true or false".
Miracles destroy faith, because they're inherently observable. If Jesus comes down and heals a leper in front of a crowd, they might quite reasonably conclude that he's telling the truth about being the son of God and they should worship him. Or at least that he has vast unexplained powers and they should do as he says to be safe.
So if God really wants faith, maybe it makes sense that miracles never happen in a way that the scientific community can verify them. If transubstantiation suddenly started working, scientists would start praying, but they wouldn't gain faith.
Because faith in existing religions only comes from indoctrination. Nobody comes to the Father except by Jesus? Well, nobody comes to Jesus except by their father... or other Christians. When allowed to find their own faith, people invent animism or materialism. Which evolve into polytheism for stability, and then... Monotheism evolved from polytheism, and now self-propagates because of tenets like hell/salvation and the stability it brought to aggressive states, allowing them to conquer en mass (pun intended).
Also, God and Jesus supposedly jumpstarted Christianity with an incredible amount of flashy public miracles. So much so that the uncorroborated, decades-later reports of such are treated as proof by people even today. (Which is actually pure faith, but it looks better to have faith in a shaky document trail than an oral tradition and groupthink.) Why was it okay to be an observable God then, but not now?