The golden rule of teaching is to move from what is known to what shall be. Lessons drawn from the fact that the seer and the scene are different include: the seer is one while the seen are many, and the seer remains relatively unchanging while the scene keeps changing continuously.
In a series of talks, Swami Sarvapriyananda lucidly unfolds the fundamentals of Advaita Vedanta presented in Drg Drsya Viveka.