Lyric discussion by piperatthewall 

Cover art for Another Brick in the Wall, Pt. 3 lyrics by Pink Floyd

the character is convincing himself that he can live without whatever he has sought throughout his life. love, and help. when he says "i have seen the writings on the wall" he is saying that he knows the whole deal. the medication doesnt work, perhaps it makes the situation worse, and it seems that whoever hes loved has left him. he knows how it is. and he is denying his own need for such things. sour grapes

I understand your point but it's still not clear to me why the image of writing in the wall was chosen.

If you ever get a chance to pick up the album the lyrics and album title are all marker written on a drawn brick wall. "Writing on the wall" I think it's kind of genius.

Ink not marker.