Syntax is a beautiful typeface, but in my experience the digital
implementation looks nothing like the specimen in Bringhurst.
For a thesis, I would recommend exclusive use of MinionPro. Headlines
can be done in all caps and small caps, or in bold. Math symbols and
Greek are included. Works very well with \usepackage{microtype}.
Eran
As a big fan of Robert Bringhurst's book The Elements of Typographic
Style, I will follow him and suggest the sanserif typeface Syntax,
designed by Hans Eduard Meier. Unlike most sanserifs, it is based on
Renaissance forms like Garamond, as is Palatino. An illustration in
his book shows how good it looks with Minion.
Bruce
