Remember your mercies, O Lord.(Psalm 24)
It is difficult to transpose this parable of the two unreliable sons from its original setting. Our Lord addressed it specifically to the chief priests and elders of his day whose infidelity was living by their own interpretation of God's commandments and obscuring God's message. Thus having promised to obey and giving reassurances, they subtly refuse to obey by substituting their own set of rules. This makes them more deceitful than the son who defies his father outright but who later changes his mind and returns to the vineyard.
Jesus lived in a very religious society, unlike our own, where the chief priests regulated the lives of the citizens by studying and interpreting the Mosaic law. However, their fatal flaw was not to be able to recognize genuine goodness - and Jesus was Goodness incarnate. Genuine holiness was obscured under the weight of rules and regulations. Even ordinary people, and Jesus points out the lowest rung of society, tax collectors and prostitutes, could recognize goodness and truth when it was presented in the person of John the Baptist, but the chief priests and elders could not.
Which son am I? Lord that I may see.