You probably know this by experience: being in this D3 world and also being in the world of the "dead", I mean the world where we go after our D3 body has done its work for one session (I guess the Buddha was the first one to experience this fully while living and really teaching about it). Schrödinger (one of the fathers of quantum phsycis) was the first one to propose a scientific theory for this - the superposition of two states which people normally consider to be separate. This theory is almost 100 years old, but it still has not penetrated into the minds of most people, even not into the mind of physicists who deal with it every day.