Writing is, above all else, about communicating ideas.
If the author confuses readers with unclear writing, then a communication breakdown occurs. This leads to three possibilities. One, the reader may reread the confusing text to better understand it. Even if this is successful, the reader is frustrated at being required to retrace his steps. Two, the reader may keep reading without trying to understand the confusing text. Since most writing builds upon what was written earlier in the work, this has an effect much like a train car derailing. Once one train car flies off the rails, each subsequent train car also flies off the rails. The following is not what we want our readers to think after reading a paragraph or essay: “That was a train wreck. I have no idea what the writer was trying to say.” Three, the reader may give up and stop reading altogether. If that occurs, then communication becomes impossible.
What does unclear writing look like? Here is a great example from a train ticket:
Time shown on timetables or elsewhere and times quoted are not guaranteed and form no part of this contract. Time schedules and equipment are subject to change without notice. Amtrak expressly reserves the right to, without notice, substitute alternate (sic) means of transportation, and to alter or omit stopping places shown on ticket or timetable. Amtrak assumes no responsibility for inconvenience, expense, or other loss, damage, or injury resulting from error in schedules, delayed trains, failure to make connections, shortage of equipment, or other operating deficiencies.
If your eyes glazed over while trying to decipher the meaning of the fine print, then you understand the need for clarity. For example, the fare conditions could have been rewritten like this for greater clarity:
Train schedules change and can be wrong. Amtrak is not responsible for any problems caused by changes to train schedules.
As a passenger, I may not be happy when reading this clearer language, but at least I understand it. Getting readers to understand your writing is the cornerstone of becoming a good writer. As the Amtrak example shows, you will be unable to always make your readers happy, but strive to never leave them confused.