Frank Jackson is a distinguished philosopher who teaches in Australia. He does “analytic” philosophy, the kind most academic philosophers in the U.S. and U.K. do. Analytic philosophers tend to take science seriously, try to offer logical arguments for their positions and often analyze the meanings of common linguistic expressions. They also generally aim for both clarity and rigor in their written work.
Being interested in the philosophy of perception, I’ve been reading Perception: A Representative Theory, one of Professor Jackson’s books. It deals with traditional philosophical questions like this: “Since science tells us that physical objects like apples and oranges aren’t really colored – they only look colored when we perceive them – and there aren’t any colors inside our brain cells – neurons don’t have tiny red and orange pictures inside them – where exactly are the colors we see?”
In a chapter called “The Existence of Mental Objects”, Jackson spends several pages discussing bodily pain, in particular, whether pains have locations in the same way that things like fruit and furniture do. For various reasons, some philosophers have denied that pains have spatial locations. So a pain in my foot, for example, isn’t literally “in my foot”.
All of which I’ve mentioned so far, simply as a preliminary to sharing the following sentence from Jackson’s book (page 84):
It is certainly not the case that “I had a pain in my foot” entails that if I had not known that the cause of my pain was not in my foot, then I would have believed that the cause was in my foot; for one way of not knowing that the cause is not in my foot is having no opinion on whether the cause is or is not in my foot, so it might well have been the case that if I had not known the cause was not in my foot, I would neither have believed that it was or that it was not in my foot.
Having read this sentence quite a few times, it is my contention that, in this case, Professor Jackson chose rigor over clarity.