Earlier quoted context omitted.
Double blind is not quite the only way to acquire knowledge. Even Karl Popper believed in astronomy.
I'm been chewing over your comment since last night, so thanks! These are just some thoughts, which I don't have a high degree of confidence in, but here goes anyway: I guess the difference between astronomy and diet is that, in my conception, at least, the systems studied in astronomy tend to be less complex than the human body and, therefore, they can be modeled relatively easily. My hunch is that this has somethin…
To needle you slightly further, though, I'd recommend you consider John Snow's investigation into cholera clusters near certain water sources in London: https://en.wikipedia.org/wiki/1854_Broad_Street_cholera_outb...
What should we make of that?
Ok, more generally...
I'm glad you're giving this some thought, because this line of inquiry (or something like it) really affected the way I think about science and knowledge. It's an incredibly rewarding line to go down, though not entirely free of frustrating dead ends.
If you find this stuff interesting, you might want to poke around a bit in 20th century philosophy. There are some (needlessly lengthy) summaries at the Stanford Encyclopedia of Philosophy, esp. under "Logical Empiricism." I hesitate to recommend that, though, it's long on history and short on significant arguments and though-provoking examples.
"Two Dogmas of Empiricism" by Quine profoundly affected the way I think about all of this. It's not an easy piece, I had to read it a few times and kept turning it over in my head for months. At first I thought it was nonsense. Then I thought it was just wrong. Then it sort of wormed its way into my head and changed a few core things I believed about knowledge. Or reorganized them. Karl Popper, Rudolf Carnap, and Wittgenstein all had profound contributions here too.
At the end of Quine's paper he says that White basically said everything important on this already in "The Analytic and the Synthetic: An Untenable Dualism." I haven't read that, but maybe it's the accessible version. One could hope.
http://www.thatmarcusfamily.org/philosophy/Course_Websites/R...