妙法蓮華經玄義 8.132

8.132

別教四門，偏而未融；圓四門，圓而且融。偏圓既殊，能通為八，圓真不二，所通唯一。譬如帝城，開四面門，四面偏門，以譬別教；四面直門，以譬圓教，偏直既殊，能通為八，帝尊不二所通唯一（云云）。

The four gates of the distinctive teaching are biased and not yet fused; the four gates of the perfect are perfect and fused. Since the biased and the perfect differ, those providing passage are eight; the perfect truth is without duality, so that to which passage is provided is only one. By analogy, the imperial capital opens gates on four sides: the four biased side-gates illustrate the distinctive teaching; the four direct gates illustrate the perfect teaching; since the biased and the direct differ, those providing passage are eight; the sovereign emperor is not two, so that to which passage is provided is only one (and so forth).