Forensic science is traditionally defined as the science of individualization, but claim that forensic scientists are able to achieve conclusions of individualization has been criticized in recent years. Many scholars hold that perfect identification of a person or object as the source of trace or mark is unachievable and that opinions about the source are always probabilistic. From the very beginning, forensic science met statistics and probability theory, and its history provides a good case study of what Bernard Cohen has called the "probabilizing revolution" in science. The emergence of DNA typing has set up a major challenge for forensic practice, opening the door to the use of advanced statistical methods and putting in question the scientific status of traditional forensic methodologies.