Expressiveness of a PL

Basically, the idea is "Expressiveness is the measure of expression. If I cannot express what I mean in a language, it is limiting expression "(from http://www.artima.com/forums/flat.jsp?forum=276&thread=198171 James Watson
).
expressiveness is not readability: James Watson Merriodoc Brandybuck

But people has different view:
There is also interrogative knowledge, exclamatory logic and imperative knowledge. You can measure expressive power of languages based on how much power they give the programmers to describe each of these knowledge types....their individual benefits don't leap out at the average person John Zabroski

I think expressiveness is the inverse of the impedance mismatch the language creates between the problem domain and the solution in code. Erik Engbrecht

expressiveness is readability: Unreadable code is not expressive. Vincent O'Sullivan

as expressive as one another. Carson Gross

The game is complexity management. Frank Wilhoit

More resources
http://www.javac.info/
http://www.bejug.org/confluenceBeJUG/display/PARLEYS/Closures+for+Java
http://www.joelonsoftware.com/items/2006/08/01.html
http://ivan.truemesh.com/archives/000637.html
http://www.talios.com/dear_java_i_need_closure.htm
http://blog.moertel.com/articles/2005/08/30/closures-and-the-professional-programmer
http://www.gafter.com/~neal/jot-wildcards.pdf