Empiricist philosophy, which posits that all knowledge is derived from sensory experience, had a profound influence on the development of psychology. This perspective, championed by philosophers like John Locke and David Hume, shifted the focus of understanding human behavior and mental processes from innate ideas or rationalism to empirical observation and experience. This empiricist approach underscored the importance of observation, experimentation, and evidence in forming knowledge about human behavior and mental processes. It laid the foundation for the scientific methodology in psychology, emphasizing the need for observable, measurable, and replicable studies. This approach was critical in moving psychology toward a more scientific and empirical discipline, shaping research methods that prioritize direct observation and experimentation to understand human behavior and mental processes.

Hermann von Helmholtz's work on sensory perception was instrumental in advancing the field of psychology, particularly in understanding how we process information from the world around us. Helmholtz's research in the physiology of the senses, especially his studies on vision and hearing, provided insights into how sensory information is translated into perceptions. His experiments on reaction time were groundbreaking, as they demonstrated that mental processes could be measured and quantified, challenging the then-prevailing notion that mental activities were too subjective or elusive for scientific inquiry. By showing that psychological processes could be studied using the same methods as in the physical sciences, Helmholtz laid important groundwork for psychology to develop as an empirical and experimental science. His work bridged the gap between physiology and psychology, highlighting the importance of the nervous system and sensory organs in understanding psychological phenomena.

The Enlightenment period, marked by an emphasis on reason, empirical evidence, and scientific inquiry, played a significant role in shaping the development of psychology as a science. This era challenged traditional notions and dogmas, encouraging thinkers to explore human nature through observation and rational analysis. The shift towards a more empirical and scientific approach in understanding human behavior and mental processes during the Enlightenment laid the groundwork for psychology to emerge as a distinct scientific discipline. Philosophers and scientists began to systematically study human behavior, moving away from speculative theory and towards evidence-based explanations. This period also saw the rise of ideas about individual rights and human dignity, which influenced psychological perspectives on human nature and the treatment of mental illness. In summary, the Enlightenment's focus on rationality, empirical evidence, and the scientific method crucially influenced the evolution of psychology from a branch of philosophy into a separate empirical science.

Dualism, particularly as advocated by René Descartes, played a crucial role in shaping early psychological thought. Descartes proposed that the mind and body are two distinct entities, a concept that sparked significant debate and exploration within the nascent field of psychology. This dualistic perspective led to the consideration of how mental processes (mind) and physical actions (body) interact and influence each other. It laid the groundwork for understanding the complexity of human behavior from both a mental and physical standpoint. The dualistic approach spurred various psychological theories that sought to explain the connection and interaction between mental states and physical experiences. This fundamental concept of dualism, despite being challenged and evolved over time, was essential in driving the field away from a solely physiological or philosophical standpoint, towards an integrated approach that considers both mental and physical aspects of human behavior.

Johannes Müller's doctrine of specific nerve energies was a significant contribution to the field of psychology, particularly in our understanding of sensory perception. Müller proposed that different sensory nerves transmit specific types of sensory information, suggesting that the nature of perception is determined by the path the sensory impulses take in the nervous system. This idea was pivotal in understanding how different parts of the brain are specialized for processing different types of sensory information. Müller's doctrine laid the groundwork for later research into brain function and localization, influencing the study of how various brain regions are connected to specific sensory and perceptual experiences. It was a key step in the evolution of neuropsychology and the scientific study of the mind, as it underscored the relationship between physiological processes in the nervous system and psychological experiences. This concept helped bridge the gap between physiology and psychology, demonstrating that psychological phenomena could be understood through the study of the physical structures and functions of the nervous system.