This work offers a systematic introduction to psychology as an experimental science, defining its subject matter as immediate conscious experience and setting out methods for introspective and physiological investigation. It surveys basic processes—sensations and perception, attention and apperception, feelings and emotions, association and memory—and treats volition and will as central active processes by which elemental experiences are combined into complex mental acts. Emphasizing laboratory technique and physiological correlation, it also distinguishes the experimental study of elementary processes from complementary cultural and historical approaches to higher mental functions, aiming to ground psychological theory in empirical observation and theoretical analysis.