The airline, government, and scientific communities have all expressed concern over the rapid development and deployment of automatic devices in transport aircraft, due mainly to the human interface, and particularly the role of automation in inducing human error. It would appear at this point that machine development has outstripped the ability of humans to dependably operate the equipment, as well as the ability of the human factors researchers to understand and cope with the problem. Although the equipment is extremely reliable, human errors in its operation occasionally create hazardous situations. In some ways, the reliability may be part of the problem: the equipment itself is so dependable that the pilot's ability to monitor it effectively is questionable. What is lacking at this time is a rationale, or philosophy of automation. This paper discusses the need for coherent philosophies of automation, and proposes several approaches.