Both religious Sanskrit and Pali use a parokṣa language, a language of implied and indirect meanings. In Buddhism the Buddha or a Zen master is using parokṣa language to explain what language cannot explain, directly, but can only be hinted at in a roundabout way. We find this kind of language especially in koans. If the adept can’t go here, he or she can forget about kensho for a while. They are not up to running speed. It will take a couple of years of hard training.
In the highest level we are communicating with someone who can directly sense the light (i.e., the animative principle). When we are with each other the bliss is so strong that you could cut it with a knife, so to speak. This is what cannot be put into words. For those not there, Buddhism can and often gets more confusing the more the conversation drags on. One of my friends, a recent graduate that I have known for several years, I can sit with and talk about this light and cover the many implications which derive from knowing it. Everyone else would think we are hallucinating—talking about something that doesn’t seem to exist.
Our everyday, commonsense language is the lowest form of language. It doesn’t work with trying to help us understand nirvana or why Joshu said, “mu.” Oh sure, we can have a conversation, but it is not profound. But for one who has had kensho, nirvana is beyond the reach of words. And “mu,” where did it come from? If the adept doesn’t know the source of “mu” he or she is lost. There is no use dumbing down Buddhism or Zen Buddhism to fit the needs of the average person. It is not going to help. The average person, over time, is going to have to pull themselves up by their own bootstraps, so to speak.