There is no art / To find the mind's construction in the face. / He was a gentleman on whom I built / An absolute trust."" Who is speaking? About whom? What is significant about this statement?

These lines are said by King Duncan of Norway.

He was talking about the betrayal of the Thane of Cawdor who had sided with the enemy and tried to take the throne of Duncan.

This speech is significant for it starts the process for the fulfillment of the three witches' prophecy.

Explanation:

These lines were spoken by King Duncan in William Shakespeare's tragedy play "Macbeth". This play's plot revolves around the greed and over ambitious nature of the character of Macbeth who from being a simple soldier later became the King of Norway by murderous means.

In Act I scene iv, King Duncan was talking about the Thane of Cawdor who had betrayed him to side with the enemy and fought against Norway. He states that it is impossible for a man to judge someone just by his appearance. he had also trusted Cawdor but as it turns out, it wasn't the same for Cawdor who chose to betray his trust and side with the enemy.

These lines and scene is significant for it starts the cycle of events that will bring upon the deliverance of the three witches' prophecy about Macbeth. With the move of making Macbeth the Thane of Cawdor, the prophecy of the witches began moving step by step, which will eventually lead to the downfall of Macbeth.