Answer:
theme is a universal idea explored in a literary work. It expresses something that is true for everyone.
C.Travelling pilgrims making the journey to Canterbury telling stories to one another
I think they saw nature in a spiritual way as the collective "Over-soul" of all the souls that create and reside in every form in creation. That means that very soul is one with and is the Over-soul, which some call God, but Dickinson and Whitman may have thought that word had to much connections to organized religion which has a different definition than they had.
