Cormac McCarthy reflects on the concept of control groups in scientific experiments, where a group subjected to conditions is compared to a control group that remains unchanged. This comparison is essential for understanding the effects of the experiment. In contrast, history lacks such control groups, making it impossible to determine what could have happened differently.

This absence of a control group in history leads to a sense of loss over potential outcomes that never occurred. McCarthy suggests that while we may mourn these "might have been" scenarios, they ultimately do not exist, emphasizing that the past is immutable and devoid of alternative paths.