Consciousness: we know it occurs when there is electrical activity in our brains, but what is this thing "consciousness" that is associated with electrical activity? When we are asleep and unconscious we are not aware of space or time. So consciousness involves awareness of space and time, or perhaps just the existence of space and time, relative to me.What do I mean by "me" ? By "me" I mean some entity,quantity,quality that is different from everything else in the world.A soul perhaps.Perhaps we all have souls made from a unique combination of masses and charges.An indestructable system of particles that goes on forever and survives Big Bangs and Big crunches. Each system would have to obey an exclusion principle which says that "no two souls can be the same in any one universe." Otherwise one person could be looking out of two bodies! And what if there is more than one soul per body! Intuitively we would think this is not the case. But if the soul is material then there can't be other versions of us living in the past or future,or in parallel universes , or else we would be consciously experiencing those universes now - like watching two television screens at once.