“Vajra is a Sanskrit word which defies translation because of its numerous connotations, but essentially vajra is an indestructible substance, usually represented by diamond.

Vajra refers to the vajra mind, the vajra nature, and the vajra prajñā. The vajra prajñā is the vajra nature which in turn is the vajra prajñā. Vajra is identical with the self-nature, the essential life force of all living beings, because both are indestructible and adamantine.

Furthermore, the eternally dwelling mind all beings have in common is the same as the vajra nature, since it too cannot be destroyed. Prajñā, as the highest form of wisdom living beings can attain, is real mark prajñā, eternally indestructible. It is therefore referred to as vajra prajñā.

Ānanda thought the false-thinking mind was the real mind. The Buddha told Ānanda, “That is not your mind. What is it? It is just the empty false appearance of dust objects before you. Those appearances manifest from your false thinking and delude your true nature. From beginningless kalpas until now you have always taken that for your mind. To do so is like thinking a thief is your son, and it makes you lose the knowledge of your eternal source. That source is the eternally indestructible precious nature, the enlightened bright mind. For that reason you appear and disappear endlessly in the six paths of the turning wheel.”

The third mind is the true suchness mind which is real mark prajñā. The true suchness mind is so great there is nothing beyond it, and so small there is nothing within it. One will find nothing smaller or larger than true suchness. The true suchness mind is the vajra mind, the real nature of every one of us.”

Hsuan Hua