大方廣圓覺修多羅了義經略疏 1.909

1.909

始知即始覺，觀行成就方能知故。本成即本覺，知與不知本是佛故。佛是究竟覺，始之與本非二覺故。

"Beginning to know" is initial enlightenment, because it can only be known when contemplative practice is perfected. "Originally enlightened" is original enlightenment, because whether known or unknown, they are originally buddhas. "Buddha" is ultimate enlightenment, because initial and original are not two illuminations.