Ian McEwan's Atonement focuses on the decisions that can change an entire lifetime. It is about the control the imagination has over situations, and the price that is paid for mistakes that cannot come undone. The problems that arise because of the main character's invalidated conclusions, cause Briony to live her life in penance, atoning for her sins.
Ian McEwan writes about the simple mistakes that all humans are bound to make. He proves through his writing about how the truth could have become clear to Briony, had she investigated further. The imagination of the young girl, causes her to jump to conclusions. She thus told the lie that separated her sister and her sister's lover, Cecelia and Robbie. The dawn of the truth shines upon the book, establishing the fact that all it would have taken to make the world right again, would have been to look for the truth.
To define ourselves, McEwan stresses that the truth is the most important object man can posses. To search for the truth would have prevented any repurcussions in Atonement, just as the truth could in any situation today. Being honest is the best trait any person can have, creating in them a more reliable individual.
The truth is rarely pure and never simple.