Depth Grammar and Surface Grammar of Religious Belief

In his book Philosophical Investigations Wittgenstein
demonstrates a methodology by which language can be
observed and investigated. The investigation"s focus is on
grammar since "essence is expressed in grammar� and
"grammar tells what kind of object anything is� (Wittgenstein
2001, §371, §373). Yet, what does the concept
"grammar" mean? Terms such as Depth Grammar and
Surface Grammar that Wittgenstein uses may be hinting to
the fact that there are (at least) two grammar levels,
however, in fact, he does not provide us with a full and
clear definition of these terms.