✔ 最佳答案
How do we know? There two process of acquiring knowledge, the ascending process and the descending process. The ascending process is by one's own efforts: researching, investigation, experimenting, theorizing, speculation, philosophizing.
The descending process is by accepting and authority (spiritual teacher, bone fide guru, no commercial guru) who have received the knowledge from another authority ( guru). The spiritual subject matters are transcendental knowledge and can not be known by ascending process, has to be accepted by the descending process. Of course, one must be situated in the mode of goodness before one can assimilate the information. In the mode of passion and ignorance (which everyone is in this material world) is almost impossible to accept this knowledge.