Arhats and Pratyekabuddhas both realize through direct perception, not through inference

The Āgama sūtras describe the pratyekabuddhas' forward deduction and reverse deduction of the twelve links of dependent arising. Although the language describing the pratyekabuddhas' contemplative investigation is rather concise and the cultivation process introduced is fairly simple, the pratyekabuddhas' practice was by no means easy; the process in between was winding and arduous. When actually engaging in contemplative practice (vipaśyanā-caryā) and deliberation, they were all in profound meditative concentration (samādhi): the mind consciousness deliberated on one side while the manas deliberated (manana) simultaneously, so of course the results were all realized through direct practice. Without meditative concentration, there is only the mind consciousness's deliberation, without the manas's simultaneous deliberation, and therefore one cannot realize—though one can understand intellectually; but intellectual understanding is of no use.

As for the pratyekabuddhas' concrete practical cultivation process, the Buddha could not disclose it in detail; the purpose was to let later people apply effort themselves and realize it through practice. Saying too much easily leads people to mere intellectual understanding, and the effort cannot be carried through properly, so it could only be stated in that simple way. Within those simple deliberations and dialogues, one must absolutely not think that the pratyekabuddhas arrived at a result merely through the mind consciousness's inference and logical reasoning—to say so would be tantamount to slandering the pratyekabuddhas. The pratyekabuddhas' meditative concentration was very profound; the mind consciousness's function absolutely cannot occupy the dominant position and cannot overpower the manas. The manas's contemplative investigation and deliberation must occupy the dominant position. The deeper a person's meditative concentration, the more the manas is employed; conversely, the mind consciousness is used more, relying mainly on the mind consciousness's imagination, inference, and speculation, and the manas cannot be put to use.

By the same token, the arhats all possessed very deep meditative concentration. In observing the five aggregates (pañcaskandha) of the past and the future, they did not use the mind consciousness's inference, nor inference (anumāna) or erroneous cognition (non-valid cognition); all was direct perception (valid direct cognition) with the manas participating. Because those physical bodies were exactly the same as the present five-aggregate body, belonging to the same category, having realized the present one, they knew the past and the future. For example, suppose there is now a batch of products that need to be inspected: because the products are all identical, sampling and inspecting just one of them reveals the condition of the entire batch. This of course does not include the case where someone has mixed in other products. On the premise that everything is exactly the same, inspecting one or a few is enough to know the whole. Therefore, the arhats' realization was all realized through direct perception: what it is, is what it is; there was no imaginative mode of thinking, no comparative mode of thinking. For those without meditative concentration, the mind consciousness's thinking by inference and erroneous cognition is unavoidable.