Even a broken watch tells the right time twice a day. However, to know that the watch is broken, we must observe it when it tells the time incorrectly rather than when it tells it correctly. This analogy is a useful way to understand the problem in modern science, because clearly there are times in which science makes correct predictions. Those who argue that science works only look at science when it seems to work correctly. To know that they are looking at a broken watch, they would have to look at it when its predictions break down — either because the prediction isn’t there, or the prediction disagrees with observation.
A common argument against the mind-body duality is that mind is an epiphenomenon of chemical reactions in the brain much like the fluidity of water is a consequence of molecular interactions. This argument seems quite appealing because if we reduce water to its molecules, we don’t see fluidity in each molecule; fluidity is only a property of the collection of molecules. The mind-brain reductionist similarly argues that the mind’s properties—sensation, thinking, feeling, willing—are features of the brain, although individual molecules that make up the brain don’t have these properties.