Dr Brent Mittelstadt's paper'Principles alone cannot guarantee ethical AI', published in the journal Nature Machine Intelligence, argues that a principled approach may not be the best way to approach ethical development and governance of AI. Consensus has seemingly emerged around a set of ethical principles for AI that closely resemble the classic ethical principles of medicine, but there are several reasons to doubt that a principled approach will have comparable impact on AI development as it has historically had in medicine. The vast complexity of AI and a lack of common aims between developers and users suggest principles may be too vague and high-level to be workable. To address these shortcomings, Dr Brent Mittelstadt calls for increased support for'bottom-up' work on ethical AI. Companies must be prepared to disclose more about how they develop and audit AI systems, and work more openly with researchers and the public.