I don't think the article explicitly explains Van Flandern's position re dark matter, but I'm quite sure he doesn't believe it exists. Here's a quote I found somewhere else:
" Take the law of gravity as an example. Some things about it, such as its inverse square nature, are intrinsic to space and time. Apparently, gravity is only inverse square for a finite distance, and then changes character (the scale where invisible “dark matter” is invented to compensate). "
From what I can tell, he seems to think dark matter is just an artificial concept used to remedy the errors introduced by the assumption that gravity obeys the inverse square law for any distance. Is it possible? I think it is. Is it true? As usual, I think the truth can only be known empirically.
But before we get to the point where it's possible to know the truth, I find it a lot more sensible to think we don't understand gravity very well than to think the universe is full of invisible stuff. However, I'm fully aware that's a layman's opinion, which is why I said I don't care much; I'd rather leave it to the experts to figure out.
As an aside, I loved this bit:
So static electric and magnetic fields are also evanescent or virtual if you wish. It follows logically, but you can never completely trust logic, that static gravitational fields behave like virtual particles or evanescent waves and propagate almost instantly
If this is established fact, doesn't it create problems for Einstein's claim against faster than light speeds? I think it makes a lot of sense that objects can't travel faster than light, but it seems the assumption that "information" obeys the same laws as "objects" is not a solid one.
Thanks for your reply, I'm looking forward for more.