"Sans pouvoir annuler le mal élémentaire en lui, bien qu'il puisse facilement le cacher; appréhendant le bien, mais incapable de l'être un vernis de conventions cachant son noyau barbare."

Simplified Meaning:

Sometimes people know what is right and good, but they find it very hard to actually do those good things because deep down, their true nature is different. They can put on a mask and pretend to be good, follow social rules, and fit in with what society expects. However, beneath this polite exterior, their basic instincts and rough, selfish traits remain untouched. For example, consider a politician who always talks about honesty and kindness in public, but in private life, he might be corrupt and manipulative. People can understand and recognize what is virtuous, yet their inner instincts might drive them to act otherwise. This means that while anyone can learn to behave properly on the outside, changing the core of who they really are is much more difficult.