瑜伽師地論略纂 3.17

3.17

「若有障緣，屬果之因，何故不障？同是有」者，謂果體有，有障能障；因體不無，障亦應障，俱是有故。量云：汝有體因，障亦應障，計體有故，如所障果。如水為果，闇能障之；盆是水因，闇亦能障。水盆俱有，闇障無差；因果不無，障障應等。翻覆比量，義准可知。設若救云：障緣亦能障於因者。亦應顯因，何故但言從緣顯果？量云：汝宗之因應從緣顯，障所障故，猶如果法。　或汝果法不從緣顯，許有障故，猶如因法。

Regarding "If there is an obstructing condition, why does it not obstruct the cause that pertains to the effect, since both are equally existent?": this means that if the substance of the effect exists and an obstruction can obstruct it, then since the substance of the cause is also not non-existent, the obstruction should also obstruct it, for both are equally existent. The formal inference is: "The existent cause in your [system] should also be obstructed by the obstruction; because you posit that its substance is existent; just like the obstructed effect." For instance, when water is the effect, darkness can obstruct it; the jar is the cause of the water, and darkness can also obstruct it. Water and jar are both existent, and the obstruction by darkness does not differentiate between them; since neither cause nor effect is non-existent, the obstruction that obstructs them should be equal. By reversing this inference, the principle can be understood accordingly. Suppose they reply to save their position by saying: "The obstructing condition can also obstruct the cause." Then it should also manifest the cause; why do you say only that the effect is manifested from conditions? The formal inference is: "The cause in your school should be manifested from conditions; because it is obstructed by an obstruction; just like the dharma of the effect." Or: "The dharma of the effect in your [system] is not manifested from conditions; because you accept that it has an obstruction; just like the dharma of the cause."