大般涅槃經義記 8.147

8.147

問曰：因緣云何為中？解有六義：一就破離斷常分別，於事分齊十二因緣次第相生，後藉前起是故非常，前能生後所以非斷，非常、非斷故名為中。

Question: How is dependent origination the middle? Explanation: There are six meanings. First, in terms of refuting and departing from the conceptual discriminations of annihilation and permanence: within the delimited scope of phenomena, the twelve links of dependent origination arise sequentially in mutual dependence; because the subsequent relies on the prior to arise, it is therefore not permanent; because the prior can produce the subsequent, it is therefore not annihilated; being neither permanent nor annihilated, it is therefore called the middle.