Matthew 13:
10 The disciples came to him and asked, “Why do you speak to the people in parables?”
11 He replied, “Because the knowledge of the secrets of the kingdom of heaven has been given to you, but not to them. 12 Whoever has will be given more, and they will have an abundance. Whoever does not have, even what they have will be taken from them. 13 This is why I speak to them in parables:
“Though seeing, they do not see;
though hearing, they do not hear or understand.
14 In them is fulfilled the prophecy of Isaiah:
“‘You will be ever hearing but never understanding;
you will be ever seeing but never perceiving.
15 For this people’s heart has become calloused;
they hardly hear with their ears,
and they have closed their eyes.
Otherwise they might see with their eyes,
hear with their ears,
understand with their hearts
and turn, and I would heal them.’[a]
Matthew 13:
34 Jesus spoke all these things to the crowd in parables; he did not say anything to them without using a parable. 35 So was fulfilled what was spoken through the prophet:
“I will open my mouth in parables,
I will utter things hidden since the creation of the world.”
I think Jesus did not speak directly most of the time and I think the reason is kind of obvious. For those who want the truth they will search for it and those who think they know it will not. So if you have some pearls of truth and also wisdom, which is a subset of what we call truth, how are you going to attract only those who will take it seriously knowing that truth is hard to bare and hard to swallow? You will need a way of filtering out those in an audience who are there to mock or there for a day of fun, or to see the new teacher for entertainment value, from those who hunger for truth and purpose. What better way that speaking in parables! This protects the perceived value of truth because a crowd and the public can run away with truth or lies for good or ill, very easily.
When it comes to philosophical truth and ultimate questions of causation and purpose and what lies beyond the great unknowns of death and the universe ect, of which Jewish thinking was not traditionally accustom to, there is an additional problem. That problem is to do with ineffable things that cannot be adequately described in words. People who come back from NDEs always have this problem because the reality they experience is not like anything they have experienced in this mode of existence and is thus ineffable. Interestingly the only way they can communicate such things are often through heavy use of similes, metaphors and parabolic narratives. This does not surprise me because ultimate and precise truth is never going to be a simple matter.
In short I think this is why we see what seems like a gradual transition between old and new testaments. It looks like God is being ever so direct in the Old Testament and it gradually becomes more opaque later on. This is just an illusion of the 21st century reader though. In reality there its opaqueness all the way through and what seems like certainly all the way through. This is because the bible was written by human beings and it is that simple. It doesn’t mean God doesn’t exist or didn’t have an influence through human beings because he does so all the time, often without people even being aware of it. The glass darkly is how it will always be in this world for good reason.