Positions in the faculty may be filled through searches for external candidates, through reappointments of existing faculty members, and, in the case of tenure-track faculty members, through promotions. The general criterion for reviewing all voting faculty candidates is exceptional quality that places candidates among the best when compared to individuals at comparable stages of career development. To this end, the school seeks to attract and retain individuals who possess a quality of mind demonstrating high levels of intelligence, clarity of expression, analytical ability, critical judgment, imagination, creativity, initiative, and industry, and a quality of character that enables individuals to support free inquiry and expression by others and to interact and work in constructive collaboration with faculty and students. In the school's evaluation of candidates, desirable individual qualities and high potential are not substitutes for a record of creative and productive achievement. Creative contributions to the field through scholarship and/or design are essential to effective teaching over time. Continued study and investigation with public exposition of research and professional accomplishments are normal obligations of faculty at Harvard.