I think that "10 percent" refers to the belief that we only use 10 percent of our brain. He is saying that 10 percent is a lot or maybe just enough to reason rationally about things like war (hence the "6 billion strong") and if more people used their thought we would be seeing the world in a more positive light.
I think that "10 percent" refers to the belief that we only use 10 percent of our brain. He is saying that 10 percent is a lot or maybe just enough to reason rationally about things like war (hence the "6 billion strong") and if more people used their thought we would be seeing the world in a more positive light.