Cannot be understood (BG and SB)

Expressions researched:
"can not be understood" |"cannot be easily understood" |"cannot be materially understood" |"cannot be perfectly understood" |"cannot be understood"

BG Chapters 1 - 6

BG 4.5, Purport:

Although Arjuna is a devotee of the Lord, he sometimes forgets the nature of the Lord, but by the divine grace a devotee can at once understand the infallible condition of the Lord, whereas a nondevotee or a demon cannot understand this transcendental nature. Consequently these descriptions in the Gītā cannot be understood by demonic brains. Kṛṣṇa remembered acts which were performed by Him millions of years before, but Arjuna could not, despite the fact that both Kṛṣṇa and Arjuna are eternal in nature. We may also note herein that a living entity forgets everything due to his change of body, but the Lord remembers because He does not change His sac-cid-ānanda body. He is advaita, which means there is no distinction between His body and Himself. Everything in relation to Him is spirit—whereas the conditioned soul is different from his material body.