Yogācārabhūmi Śāstra, Volume Thirty-Four (Thirty-Eight)

Original text:如是比度作意力故。由灭坏行。于彼诸行刹那生灭。灭坏无常而得决定。于如是事得决定已。复于他世非所现见。诸行生起。应正比度。云何比度。谓诸有情现有种种差别可得。或好形色。或恶形色。或上族姓。或下族姓。或富族姓。或贫族姓。或大宗叶。或小宗叶。或长寿命。或短寿命。言或威肃。或不威肃。或性利根。或性钝根。如是一切有情差别。定由作业。有其差别方可成立。非无作业。如是有情色类差别。定由先世善不善业。造作增长种种品类。

Explanation: Because of the power of intensified attention (adhimātra-manaskāra-bala) of inference, from the various formations of destruction, one observes that all formations arise and cease in each instant, being destroyed and impermanent, and thereby reaches the conclusion: all formations are subject to change and impermanence. After reaching certainty regarding these matters, since one cannot directly perceive the arising of formations in past and future lives, one should therefore engage in correct inference. How does one infer? The various differences presently observable among sentient beings can be seen: some have good physical appearance, some have evil physical appearance; some come from noble family lineages, some from lowly family lineages; some come from large clans, some from small clans; some are long-lived, some are short-lived; some speak with dignity and solemnity, some speak without dignity or solemnity; some have sharp spiritual faculties (indriya), some have dull spiritual faculties.

All such differences among sentient beings can only be established because there are differences in the karmic actions they have performed, not because there are no karmic actions performed. The differences in the physical forms and types of these sentient beings are definitely due to the wholesome and unwholesome karma created in previous lives, which has grown and produced the various kinds of differences among them.

Correct inference is based on what has already been directly perceived and settled in the mind, conducting comparative deliberation (manasikāra). If it is not based on direct perception, then the comparison and deliberation is incorrect inference; incorrect inference is not encompassed by wisdom, whereas correct inference yields wisdom.