I have read and reread this message, as Jesus seems to be telling us something more. I believe the more is about the purity of Christ. The shadows would be the imperfection of the message. We may all find it difficult to live the pure truth of Christ every minute of every day but we must be, WILLING, to try so as to be able to be HIS light to others.
1 John: 5&6
This is the message we have heard from Him and declared to you: God is light, in Him there is no darkness at all.
Deuteronomy 30:14
No the Word is very near you, in your mouth and in your heart so you may obey It.
When we are purely willing to live His Truth we will find that the Truth is already in us. When you advise people as to the direction they should take towards God you know that they will realize you are speaking Truth.
We follow the Truth of Christ through the Magisterium of the Catholic Church.