I can explain it with science, deeper to molecular level and also I got some new idea while pondering over it. Life is a state of mind means every person has its own thinking. Why peoples have difference in thinking or thoughts beside having same structures that is because of the difference in hormonal level and different chemicals. What are chemicals? Just because of the difference in chemical or molecular composition. Molecules are formed due to different atomic composition. Atoms are different because of the difference in nucleus, protons and neutrons. Similarly, every proton is different for every different atom same goes for electrons and neutrons. Even atoms having same protons and neutrons possesses a difference in them. Like we cannot say that two similar sodium or aluminum atoms exist.

link
http://www.ijser.org/onlineResear