This song, like many other pink floyd songs, should be listened to, when high. I feel the song unfolds a totally new meaning when listened to in a state of trance. "Wish you were here" is an one-end conversation between two versions of the same person, our real selves, the one who is stuck in the quagmire of the daily life, and the higher self, the one who is outside this circle of influence of the external stimuli.
Day in day out we try to untangle the shackle life has put on us, we try to solve the mystery of the cycle of happiness and sorrow in our own way, we try to fit things in our definitions of black and white, good and bad, heaven and hell, and this constant endeavor makes us believe we can actually differentiate between every thing that surrounds us. Then comes a state which is above everything. A state of mind where nothing really matters, where words seem fake, the black and white world troubles no more and we realize how stupid we were to have cared about the small things and in the process made our lives small.
I will explain this conversation, (or monologue) from the point of view of two forms,
Form 1 - The normal us, or the conscious form.
Form 2 - The higher form, the sagacious form.
"So, do you think you can tell, heaven from hell, blue skies from pain, can you tell a green field, from a cold steel rail, do you think you can tell?" this part of the song is a mockery thrown by form 2 upon form 1. He mocks him by saying, "how silly you were to have cared about good & bad, black & white, when nothing actually matters. So what you can tell what is good and what is bad, how does it matter? that, what is good to you can be bad for me. How silly were you to have thought that you know the lines of difference, when everything in this world is absolute."
"Did they get you to trade, your heroes for ghosts, hot ashes for trees. hot air for cool breeze, cold comfort for a change, did you exchange a walk-on part in the war, for a lead role in a cage?"
We all sell ourselves everyday. To find a momentary happiness, to achieve a short-lived goal, we weigh ourselves on the other side of the balance. They trade us daily and we sacrifice in the process. We sacrifice the things we love, the things that make us the man we really are. We tie the knot so tight that we forget it chokes us dead. Here form 2 feels sorry for form 1 and he sympathizes with form 1 and asks him were you put into trade too?.
"How I wish, how I wish you were here, we're just two lost souls, swimming in a fish bowl, tear after year, Running over the same old ground.
What have we found? The same old fears.
Wish you were here.."
Now form 2 asks form 1 to set free of all the attachments that bind him to the ground and stops him from flying away. He tells him that they have lived in the same fish bowl (body) for many years and have seen the same things and have developed the same fears, but form 1 has been affected by those fears and that is why he suffers, on the other hand, form 2 remains undeterred as for him the small things in life does not really matter. So form 2 wishes form 1 to come to his state.