The first words of this verse should be rendered thus: Of a truth, Master, thou hast well said that he is one. In the remainder of the scribe's answer we find a different word used in the Greek for" mind," or "understanding," from that just used by our Lord.
In our Lord's answer the word is διάνοια. Here it is σύνεσις. Both words are well rendered by "understanding." It is an act of understanding. It is the thought associating itself with the object, and "standing under" it so as to support it.