From the earliest time to the present days, viewpoints concerning human nature were vehemently contended among prominent philosophers. Mencius believed human nature is good, and people are naturally inclined toward virtue. While, Xunzi deemed human are basically evil who need to be changed by man-made.
As it is widely known, human nature is that indestructible matrix upon which the character is built. Accordingly, to a large extent, the basic nature of human beings cannot be changed. On the other hand, each of us is naturally endowed with diverse both qualities and personalities, which makes us unfold an apparently distinct character. Then, it is hard for one to change his nature fundamentally. Regardless of whether nature is innate or habitus acquired, they were both a consistently developing courses that cannot be easily changed in a short time. Last but not the least, external influencing factors, like religious, education and even social institutions can merely direct our nature on account of the most limited control. Thus, it is only the surface that is capable of alteration, improvement and refinement.
In a word, the basic nature of human beings does not and cannot change and also no one can fundamentally change his nature in the short time. But people can make it perfect.