Charles Hope (UK) is a former Director of the Warburg Institute and will discuss the tension that exists between connoisseurship as a type of expertise acquired by long experience and as an activity based on the use of historical evidence and reasoned argument. Will claim that, in practice, these two aspects are often in contradiction to one another, and that many connoisseurs have been unable or unwilling to provide clear arguments about how they have reached their opinions. Too often, judgements about authorship are decided by appeals to authority, and almost by vote, rather than by evidence.