"We identify our shadow, in other words, with that visible shape we see projected on the pavement or the whitewashed wall.  Since what we glimpse there is a being without depth, we naturally assume that shadows themselves are basically flat-and if we are asked, by a curious child, about the life of shadows we are apt to reply that their lives exist only in two dimensions." p.16

"The apparent gap between myself and that flat swath of darkness is what prompts me, now and then, to accept its invitation to dance, the two of us then strutting and ducking in an improvise pas de duex wherein it's never very clear which of us is leading and which is following." p.17

 Taken from the shadow-depth chapter in this book. I am slowly reading chapter by chapter and absorbing.  Abrams suggests in this chapter that our shadow is actually within that space existing between our bodies and that flat, dark shape we observe projected onto a service.  Apparently at high noon our shadow sinks into us-the time, of course, when no shadow is cast- which causes people to become tired and consequently take siestas.