The reason why there are hardly ever completely knock-down arguments, except between very like minded philosophers, is that philosophers, unlike chemists or geologists, are licensed to question everything, including methodology.

J. J. C. Smart, ‘Ockhamist Comments on Strawson’, in Anthony Freeman (ed.), Consciousness and its Place in Nature: Does Physicalism Entail Panpsychism?, Exteter, 2006, pp. 158-159