NavList:

  Frank, you wrote:

“But this brings us to  an interesting conundrum... How do you know that any "mainstream" topic in  science is not "nonsense"? Let's take, as a random example, fluid dynamics. It's  mostly classical physics in the extreme, and I can't think of any reason to be  skeptical of its basic conclusions --it's about as mainstrem as you can get. But  why do you believe in it as a science and not, to pick another random example,  homeopathic medicine?? Have you studied it yourself (and if you have, pick  another comparable example)? Although rational thought and personal  experimentation are a big part of science, in the end, you and I cannot  personally test each and every theory. So do we adopt an absurd agnosticism in  which subjects outside our personal experience are unknown to us? Or can we  accept that there is a certain division of labor in science, and if I find  something nonsensical, you also have a basis for finding it nonsensical? I  believe that this is actually what people do in the real world of science, but  it's a bit removed from the utopian vision of scientific proof. As I say, it's a conundrum.” 

Both fluid dynamics and (to a lesser extent) homeopathic medicine lend themselves to rational explanation. I accept as prima facie evidence the work others have put into understanding them. Other topics seem beyond science. To dismiss them as nonsense without evidence seems a travesty of rationality. I am intrigued by those who profess to be rational yet proudly claim to be atheist. How do they know? I always wonder. Isn’t their lack of faith as equally blind as that of those who profess it? It seems to me that agnosticism, far from being absurd, is the only rational response to the unknowable. I agree its a conundrum.

Navigation owes a lot to astrology, as many early astronomers were inspired by astrological motives. Even now, it seems, astrology continues to shine a light for us, to wit the current topic.