It is common to consider the founding year of psychology to be the year in which psychology became a separate science. According to Hergenhahn (2009), this approach is unsatisfactory for two reasons: (1) it ignores the vast philosophical heritage that shaped psychology into the kind of science it eventually became; and (2) it omits important aspects of psychology that are outside the realm of science. Since the mid-19th century, psychologists have incorporated the scientific method into their work, however, the work of many psychologists who did not embrace the scientific method before the mid-19th century cannot be ignored. According to Kendra Cherry, before 1879 there were many potential contributors to the beginning of what is often called "modern science", the ideas of the French philosopher René Descartes are important for science but especially for psychology. During the 17th century, he worked to answer the question "Are the mind and body the same or are they different?" and this led to the development of Cartesian dualism, which is the idea that the mind and body are different, but that the mind can influence the body and the body can influence the mind. This stated that the mind and body were two separate entities that interact to form the human experience. Descartes is best known for his principle that thoughts exist, known as cogito ergo sum, since thoughts cannot be separated from him, he existed. Furthermore, he stated that if he could doubt, then something or someone must also doubt, so the very fact that he doubted proved his existence. Questioning the mind is an important aspect of psychology, so this may have been the beginning of psychology. Hergenhahn (2009) also stated... ... middle of paper ...... and humanities (philosophy, languages, music and art). While early philosophers relied on methods such as observation and logic, today's psychologists use scientific methodologies to study and draw conclusions about human thought and behavior. Physiology also contributed to the future affirmation of psychology as a scientific discipline. Early physiological research on the brain and behavior had a dramatic impact on psychology, ultimately contributing to the application of scientific methodologies to the study of human thought and behavior. The ancestry of psychology is important, as they made significant contributions to the foundation of psychology even though they did not use the scientific method. Many other questions still debated by psychologists today, such as the relative contributions of nature versus nurture, are rooted in these early philosophical traditions.