Shoyoroku - Case 49: Tozan and the Memorial Service

When Tozan held a memorial service for Ungan before his portrait, he mentioned
the episode with the portrait [1]. A monk came forward and asked,
  "When Ungan said, 'Just this!' what did that mean?"
Tozan said,
  "At that time, I almost misunderstood my master's meaning."
The monk said,
  "I wonder whether or not Ungan really knew that IT is."
Tozan said,
  "If he did not know that it is, how could he say like that? If he knew that
   it is, how did he dare say like that?"

[1]: Tozan was still a young monk under Ungan. One day, when he was leaving his
     master, he asked Ungan, "After your passing, if I am asked by someone
     whether I have your portrait, what should I answer?" Ungan was silent for
     a while and then said, "Just this."

