The text investigates the biological foundations of mental phenomena, arguing that psychology must root itself in organismal and social conditions. It presents four essays on the nature of life, the nervous mechanism, animal automatism, and reflex action, combining physiological description with philosophical critique. The author emphasizes a biological rather than metaphysical or purely mechanical viewpoint, warns against speculative assumptions such as imaginary anatomy and the unexamined primacy of the nerve-cell, and proposes extending competition principles to tissues and organs. The work seeks to reconcile mechanical explanations of movement with biological complexity and to show how physical processes relate to mental aspects without reducing one wholly to the other.