四道

The Dao or road means the nirvana road; the 'four' are rather modes of progress, or stages in it:

(1) 加行道 discipline or effort, i. e. progress from the 三賢 and 四善根 stages to that of the 三學位, i. e. morality, meditation, and understanding;

(2) 無間道 uninterrupted progress to the stage in which all delusion is banished;

(3) 解脫道 liberaton, or freedom, reaching the state of assurance or proof and knowledge of the truth; and

(4) 勝進道 surpassing progress in (sa) dhyāni-wisdom. Those four stages are also associated with those of (sa) srota-āpanna, (sa) sakṛdāgāmin, (sa) anāgāmin, and (sa) arhat.