I have believed for a long time that human nature is a reciprocity of what is inside the skin and what is outside: that it is definitely not "rolled up inside us" but our way of being one with our fellows and our world. I call this field theory.
It has become accepted doctrine that we must attempt to study the whole man. Actually we cannot study even a whole tree or a whole guinea pig. But it is a whole tree and a whole guinea pig that have survived and evolved, and we must make the attempt.