Mike Burke wrote:I'm less interested in Luke 1:35 than I am in the general rules.
How do we know when "kai" means "and" and when it means "even."
Is there any reliable rule of thumb?
No, to put it very bluntly, there aren't. You have to know Greek well enough from lots of reading (or conversation) to have developed a good sense of how the contextual elements in any particular construction point to one usage rather than another.
You
could endeavor to read carefully through the
very, very lengthy entry on καί in BDAG, carefully study
all of the examples there, and so acquire a fully-nuanced grasp of the considerable range of this little adverb/conjunction. You could try to do the same in one of those little
vade mecum pocket lexica like that of Barclay Newman, but I really don't think you'll find anything there (or elsewhere) that could be called a "rule of thumb" for καί. It is something that one learns through repeated exposure to variant usages and then discerns, as Hume put it, by "custom and habit of confident expectation."
Euclid said that there really is no "royal road" to Geometry -- the same is true about ancient Greek.
Carl W. Conrad
Department of Classics, Washington University (Retired)