Conceptual Art

Buchloh presents both Sol LeWitt and Robert Morris as conceptual artists. I see how Lewitt's work embodies this movement and theme - he combines visuals with linguistics, creating conflicts and challenging his viewers. Morris plays with different senses in his productions using a strategy of "perceptual withdrawal", which is definately cool but I don't see how it is necessarily conceptual art. I guess our language is a sense -we rely on it to communicate, document, and think, but it seems like since it is sooo much more integrated into human culture and civilization, challenging language is a much bigger deal than, say, removing visual cues and replacing them with audio stimuli. Some one who is blind and needs to rely on their other senses more is more typical and easier for an audience to grasp than someone who has lost/never had any sense of language.

When the author is discussing the squares and cubes, he talks about the importance of the painting's transperancy. How it, quite literally, makes a piece conceptual art by forcing a view into the frame, support, etc of the work. It addresses the history of it, the manual work done to install it, and the traditional how-to of the process. My question is - many other works we've looked at have done this as well - from visual to performance pieces. Are all those considered conceptual art pieces as well? Is this movement generally regarded in reference to a time frame or the entire idea (which comes in waves and jumps through art history)?