Rev. Sekishi's talk on Building a House and the Four Seals: the four characteristics (or "seals") are sometimes seen as a sort of "litmus test" to see if a teaching reflects true Buddha Dharma. But they can also be viewed as part of the core teachings of Buddhism:
All compounded things are impermanent
All emotions are Dukkha
All phenomena are empty; they are without inherent (or "self") existence
Nirvana is beyond extremes / concepts / description
Further reading and discussion for this talk are available on the Treeleaf forum:July 5th-6th, 2019 - OUR MONTHLY 4-hour Treeleaf ZAZENKAI! - featuring Sekishi ! »