[2157] A phenomenon (dhamma) with an external object (bahiddhārammaṇa) is a condition for a phenomenon with an external object by way of decisive-support condition (upanissaya-paccaya): proximity decisive-support (anantarūpanissaya) and natural decisive-support (pakatūpanissaya).
Natural decisive-support: contemplation of impermanence (aniccānupassanā), contemplation of suffering (dukkhānupassanā), and contemplation of impersonality (anattānupassanā) with an external object are a condition for contemplation of impermanence, contemplation of suffering, and contemplation of impersonality with an external object by way of decisive-support condition.
English translation from the Pali (Siam Raṭṭha edition) — under review, not for citation.