It has been said that following the Buddha's death, the teachings (dharma) have gone through three successive periods of degeneration.  In the period of the true dharma (shobo), which lasted 500 to 1,000 years after the Buddha's death, the dharma was properly practiced and enlightenment could be attained. In the period of the semblance dharma (zobo), lasting 1,000 to 500 years, the teaching was practiced but enlightenment was no longer possible. In the period of the last dharma (mappo), lasting 10,000 years, although the teaching still existed, there is no practice or enlightenment.  In Japan, it was believed that the last period began in 1052 A.D.. The idea of mappo heavily influenced the Buddhist movements during the Kamakura Period.

Regarding this concept, Zen Master Dogen instructed,

Many worldly people say, “I desire to practice the Way, but the world is in this last degenerate period and I have only inferior capabilities.  I cannot endure the formal practice which accords with the dharma. I want to find an easier way which is suitable for me, make some connection with the Buddha now, and attain enlightenment in the next lifetime.”  

This is entirely wrong. Categorizing the three periods of time—the true dharma, the semblance dharma, and the last dharma—is only a temporary expedient. Monks in the time of the Buddha were not necessarily outstanding.  There were some who were incredibly despicable and inferior in capacity. Therefore, the Buddha established various kinds of precepts for the sake of evil and inferior people.  

Without exception, everyone is a vessel of the buddha-dharma. Never think that you are not a vessel.  If you practice according to the teaching you will gain realization without fail. Since you have a mind, you are able to distinguish good from evil. You have hands and feet, and therefore lack nothing for practicing gassho or walking. Therefore, in practicing the buddha-dharma, do not be concerned with whether you are capable or not. Living beings in the human world are all vessels (of the buddha-dharma). It would not be possible if you had been born as an animal or something else.  

 Students of the Way, never expect to practice tomorrow. You should practice following the Buddha only today and this moment.