What does Mark 8:17 mean?
Jesus is trying to teach important spiritual truths about false teaching and an individual's responsibility to evaluate religious leaders. Yet, the disciples discuss why they do not have enough to eat. Jesus abandons His intended lesson and goes back to the basics, using the Socratic method of teaching to lead the disciples to accept what they should already know. His first goal is to help them realize how hard-headed they are being."Perceive" is from the Greek root word noeo and means to catch an idea, think about it, and then act on it. "Understand" is from the Greek root word suniemi and means to reconcile different data points to come to a conclusion. Jesus is accusing the disciples of being unable to process what they have experienced.
"Hearts" is from the Greek root word kardia. It is the center of life, emotions, impulses, desire, and ultimately character. "Hardened" is from the Greek root word poroo and literally means to be covered with a thick callus like an elephant foot. Metaphorically, that callus covers the heart and mind so a person is mentally and spiritually dull.
This charge is more serious than merely being mentally incompetent. Having a hardened heart is at least partially a choice. Jesus is challenging the disciples to consider if they are intentionally rejecting the teaching He has given them. They have received more training than anyone else (Mark 4:11), and yet they are in danger of rejecting Jesus and who He is just like the Pharisees and Herodians who fear Jesus for His threat to their power.