妙法蓮華經文句 1.58

1.58

觀心釋者，觀因緣所生心，先空、次假、後中，皆偏覺也；觀心即空、即假、即中，是圓覺也（云云）。

Explaining in terms of contemplation of mind: contemplating the mind arisen through causes and conditions—first as empty, next as conventional, and afterwards as middle—are all partial awakenings; contemplating the mind as identical to emptiness, identical to conventional designation, and identical to the middle is perfect awakening (and so on).