The principal Spirit of Dharma. I read this from one of the zen story book. I thought this will help you.

One day one disciple asked his monk master " What is the main spirit of the Dharma ?

Monk master replied "we do no harm to others ; moreover we must propose to do the least good whenever possible".

The answer didn't satisfy the disciple; He replied to monk master, Master is it not so simple ! All three Year old know what you are talking about

Monk master replied as Even if a three year old knows it, an eighty year old is not able to apply these words.

My learning today from this is : The simplest words to explain are sometimes the most difficult to apply. Implementing words of great wisdom requires great wisdom.