Some say that we all possess buddha nature and that the nature of the mind is pure.
That doesn't mean that there is a permanent 'thing' called buddha nature
but it means that once the clouds are removed, the sun is still shining the same as it always was.
in other words, the mind's original nature is perfect clarity, and one merely needs to remove what is obscuring the realization of that fact.
others say that the nature of the mind is impure, and only through cultivating virtues and undergoing rigid training can one be free from suffering and attain realization.
I tend to agree with the first paragraph. Prince Siddhartha also possessed an intrinsically enlightened mind and he went through all kinds of crap before he realized it, but once he saw it, it never went away.
'never went away' means he was fully enlightened.
Profile Picture: "The Foaming Monk"
The Chinese characters are Fo (buddha) and Ming (bright). The image is of a student of Buddhism, who, imagining himself to be a monk, and not understanding the true meaning of the words takes the sound of the words literally. Likewise, People on web forums sometime seem to be foaming at the mouth. Original painting by P.Volker /used by permission.