Statement from Electricity and Magnetism (Edward Purcell):
Perhaps you still want to ask, what is an electric field? Is it something real, or is it merely a name for a factor in an equation that has to be multiplied by something else to give the numerical value of the force we measure in an experiment? Two observations may be useful here. First, since it works, it doesn’t make any difference. That is not a frivolous answer, but a serious one.
Second, the fact that the electric field vector at a point in space is all we need know to predict the force that will act on any charge at that point is by no means trivial. It might have been otherwise! If no experiments had ever been done, we could imagine that, in two different situations in which unit charges experience equal force, test charges of strength 2 units might experience unequal forces, depending on the nature of the other charges in the system. If that were true, the field description wouldn’t work.
Couldn't understand the sentences in bold. Especially, how is field description related to it (see the last sentence in italics)? Why wouldn't it work?