Through others we become ourselves.
Lev Vygotsky, Language and Thought
Vygotsky has been a huge influence in developmental psychology and, alongside Jean Piaget, is responsible for much of the foundation for many educational practices today.
His concept of the "zone of proximal development" in particular is worth keeping in mind. It simply refers to the distance between that we can do and that we can't: the space in which we need the help of others to proceed.
It is the capacity for nurture that sets humans apart, and without knowledge shared we would be limited to what we can learn on our own. We each live much of our lives in Vygotsky's zone, and as such it's worth considering how much time we spend helping others through theirs.
Perhaps most interestingly, this particular concept mirrors the 'magical mentor' stage of the hero's journey. More evidence of myth reflecting the human experience.
On a related note, one of the ways we can proceed through the ZPD is with our inner voice, or as Vygotsky called it self talk