At the weekend we enjoyed a mindfulness morning on the Sutra on the Full Awareness of Breathing. Pete mentioned the Three Doors of Liberation in the context of breathing exercise twelve.
Here are two useful videos of Thay explaining these concepts. They come from video recordings of Dharma talks during the Breath of the Buddha retreat at Plum Village in 2006.
First one is on Emptiness
Second on is on Signlessness (which we didn’t cover) and Aimlessness (from 11 minutes in) which we did – a bit!