There are two parent disciplines of scientific psychology: philosophy and physiology. Even though Aristotle is credited with launching the study of life that eventually became the science of psychology, it was not until 2,200 years after he lived that the sciences emerged from the field of philosophy. Psychology gained its independence from philosophy when researchers started to examine and test sensations and perceptions using scientific methods. Philosophy, on the other hand, is not held to the scientific requirements of psychology. Philosophers, on the other hand, do not collect data to test their ideas. The practice of psychology emerged first, followed by science.