According to the teachings, what is the fundamental cause of fear and seeing the world as deceptive?

The fundamental cause of fear and the deceptive appearance of the world is ignorance, also referred to as Avidya. As explained in Chapter 50, this ignorance acts as a veil, covering our knowledge and causing us to misperceive reality. The text uses the analogy of a rope on a path in dim light; though it is just a rope, it appears as a venomous snake, causing immense fear. This appearance of the snake is purely a product of ignorance, and without its removal, the mind cannot become fearless. This same ignorance is the root-foundation of the visible, deceptive world.