This document explores the essential connection between life and the process of reacting, which is fundamentally predicated on an organism's sensitivity. The author posits that the quality of life increases with sensitivity; however, this heightened perception requires a focused direction that often necessitates the disregard of other environmental stimuli. In sub-human life forms, behavior is largely governed by instincts and action systems triggered by specific impulses. These instincts do not function as a logically integrated system but are instead based on a historical reaction foundation. A central theme of the text is the observation that instinctive reactions can become ineffective or entirely obsolete—serving as biological relics whose original purpose has been lost. This phenomenon occurs when environmental circumstances undergo rapid transformations that outpace the evolution of fixed behavioral responses. Ultimately, the text provides a philosophical and biological analysis of how sensitivity and historical adaptation influence survival, warning that rigid adherence to outdated instinctual patterns can lead to nonsensical and maladaptive behaviors in a changing world.