Perhaps the most convincing evidence of this oneness is that up to 40% of people have what are called "unitive experiences" or experiences of expanded consciousness at some time in their life. Here's a typical example:
"After a while, I realized that I had expanded. I was no longer a small discrete consciousness located in my head - I encompassed the whole valley. I was HUGE. I was part of everything - or rather everything was part of me. I was ancient and unbelievably powerful. It was wonderful." Read more.