déjà vu -- Crosby Stills, Nash & Young

One Two Three Four  If I had ever been here before
I would probably know just what to do  Don't you?
If I had ever been here before on another time around the wheel
I would probably know just how to deal  With all of you

And I feel  Like I've been here before  Feel  Like I've been here before
And you know it makes me wonder  What's going on under the ground,
Do you know? Don't you wonder?  What's going on down under you
We have all been here before, we have all been here before
We have all been here before, we have all been here before         (sing365)

David Crosby  "I'm one of those people who thinks we go round again. The Buddhists have got it right - it's a wheel and we get on and get off. I think life energy gets recycled. That's why I wrote Déjà Vu."  

"The law of conservation of energy applies: life force just doesn't go away. The identity print gets wiped, mostly, but sometimes there's a ghost print and some stuff hangs around. How else can I explain knowing how to sing harmonies at age six or knowing how to sail a boat the first time I got in one? And having a persistent delusion, all my life, of having been somebody else before."                                                                                            (songfacts) 

Déjà vu is a French phrase meaning "already seen  ", and it refers to the experience of feeling sure that one has witnessed or experienced a new situation previously.         (wikipedia) 

                               

  what is   déjà vu   ?