I think I'm beginning to see the point of this thread. It seems that by "the doctrine of parables" GWH means "what the scriptures teach on the purpose of God using parables". And there seems to be a disagreement over whether God's parables are intended to hide truth from the non-elect, but God grants divine gnosis to the elect so that only they can understand them; or are they intended to inform, but people blind
themselves from understanding them because of their preconceptions and habits that are antagonistic towards the evident meaning of the parables.
GWH's aim seems to be to discern, by looking at all the parables themselves, whether they themselves reveal the purpose of their use. You seem to strongly lean towards God's purpose in using them being to hide truth from the non-elect, based on the above text From Mark (and others like it). You seem to see two contradictory affirmations in scripture: God wants all to be saved by faith; but God also intentionally hides the truth that allows saving faith from certain people so they cannot repent and believe to be saved. You seem to advocate embracing the contradiction and surrender to the cognitive dissonance. But maybe the one of your contrary affirmations is not actually what the Bible is saying. Maybe the Bible does not say that God is deliberately hiding the truth from some so that they cannot repent and believe and be saved. Maybe those who are hostile to the truth would be a continual aggressive disruption to the ministry of God's word toward those who are open to its truth, if the hostile ones understood the claims being made that they would truculently refuse even to consider, so in order to create a calmer learning space for the open-hearted, God's prophets present God's truth in the form of mundane stories that the hostile consider beneath their intellect to spend time interpreting. So, they leave to do something they consider more productive, leaving the teaching space to Jesus and those who love and hunger for goodness and mercy.
Mark 4:10-13
And when He was alone, they that were about Him with the twelve asked of Him the parable. And He said unto them,
Unto you it is given to know the mystery of the kingdom of God: but unto them that are without, all [these] things are done in parables:
That seeing (present active participle) they may keep on seeing (present active subjunctive), and may not keep on perceiving (present active subjunctive);
and hearing (present active participle) they may keep on hearing (present active subjunctive), and may not keep on understanding (present active subjunctive);
Jesus uses the present subjunctive here. The present subjunctive indicates an action that is a continuation of an action that has already started. So, some of those outside began to understand, but stopped understanding; and others outside began to understand and kept on understanding. Two options, hence the subjunctive.
The aorist subjunctive would indicate an action beginning to occur. Had Jesus used the aorist subjunctive, He would have been saying that SOME might not start perceiving, and SOME might not start hearing.
Also we should note that Jesus does not use the indicative and say -
That seeing they will keep on seeing, and will not keep on perceiving;
and hearing they will keep on hearing, and will not keep on understanding;
In other words, the intention is not that ALL outside will not perceive and will not understand. The intention is that SOME may
keep on perceiving and keep on understanding, and SOME outside may not keep on perceiving and keep on understanding. This does not equate to an intention that SOME would never even start to understand the parables. We see that the Pharisees understood the parable of the tenants in the vineyard, and that it was against them, but they closed their minds to its warning that they should repent from their murderous hatred of the Son.
lest at any time they should start converting (aorist active subjunctive), and [their] sins should start to be forgiven (aorist passive subjunctive) to them.
Here we are told why those who do not keep on perceiving and do not keep on understanding do not keep on perceiving and do not keep on understanding. They stop perceiving and understanding because they refuse to make the changes in their behaviour that would release forgiveness upon them.
So, this text does not at all say that God intentionally withholds perception and understanding from anyone. It says that some suppress their nascent perception and understanding of parables because the parables message begins to challenge habitual behaviour they are unwilling to consider changing. even if changing will gain them forgiveness.