The power of the grid is to lift the designer outside of the protective capriciousness of the "self" by providing an existing set of possibilities, a set of rules.
I choose this quote as it is about grids which I am interested in as 'the' symbol for our culture. Grids are everywhere in culture: In buildings, roads, screens. Pixels are a grid. Fonts and Writing are a grid. Perspective is a grid. Often grids are not so visible or obvious, but we are nearly always looking at a grid unless we are looking a nature. Lupton writes that grids "can be seen as metaphors for the human need to make sense of the world and to position ourselves in control of it."
For a graphic designer, grids are essential, even if we are trying to challenge their ubiquity. "A grid is the graphic design equivalent of a building's foundations." The quote suggests this is a very useful thing, as though we might be a little lost as designers without a grid to start from. The Capriciousness of the self that Lupton talks about suggests a certain instability and unaccountability. Perhaps she is suggesting the wildness of the human imagination can be a little out of control with out a structure to reign it in. Perhap grids are what allow us to communicate with each other as we have all grown up with grids and understand them. For example a font that strays too far from a grid, may be illegible. A piece of music that does not adhere to or imitate music structure, may just sound like unpleasant noise.