Primary literature is any literature that flows directly from an expert
source. Thus, a book by S. J. Gould is primary. A book that purports to
summarize Gould is secondary. Someone relying on the latter is using a
secondary source. But someone reading, and quoting from the former, is using a
primary source.
Denis is, I think, merely confusing primary with "technical." If Gould writes
an article for a scholarly journal within his field, this is technical (read:
unpopular). This is beyond the amateur without a good deal of effort.
But when Gould sets out to explain his theories to the layman, and does so in
a book, it is primary literature which the layman can read and analyze.
So, dear friends, Phillip Johnson is NOT criticizing secondary sources.
Denis, you almost slipped that one past us!
Jim