Phenomenal objects are pure in themselves, it is our relationship to those objects which is impure.
Ordinarily, we divide into bad and good. The division may be for any reason. It may be hygienically, morally or in any other way, but we divide life into two - good and bad. And ordinarily, whenever we say purity we mean goodness - the bad qualities should not be allowed and the good qualities should be there. But for Tantra this division of good and bad is impure. Tantra does not look at life through any dichotomy, any duality, any division. Then what is meant by purity in Tantra? Tantra says that to divide is impure and to live in non-division is purity. Or to discriminate, make dualistic distinctions is impure. So for Tantra purity means innocence - undifferentiated innocence A child is there; you call him pure. He gets angry, he has greed, so why do you call him pure? What is pure in childhood? Innocence! There is no division in the mind of a child. The child is unaware of any division into what is good and what is bad. That unawareness is the innocence. Even if he gets angry, he has no mind to be angry, it is a pure and simple act. It happens, and when anger goes, it goes. Nothing is left behind. The child is again the same, as if the anger has never been there. The purity is not touched; the purity is the same. So a child is pure because there is no mind.
From Tilopa's Ganges Mahamudra:
"Leave the polluted water of conceptual thoughts in its [natural] clarity. Without affirming or denying appearances, leave them as they are. When there is neither acceptance nor rejection, [mind] is liberated into mahāmudra.....
"The practice of Mantra and Paramita,
Instruction in the Sutras and Precepts,
And teaching from the
Schools and Scriptures will not bring
Realization of the Innate Truth.
"He who keeps Tantric Precepts
Yet discriminates, betrays
The spirit of Samaya.
Cease all activity, abandon
All desire, let thoughts rise and fall
As they will like the ocean waves.
He who never harms the Non-abiding
Nor the Principle of Non-distinction,
Upholds the Tantric Precepts."