Nope, it doesn't. It may encourage it, but by no means is it required. Common Lisp was the first standardized object oriented language, actually (https://secure.wikimedia.org/wikipedia/en/wiki/Common_Lisp_O...).

You can write Lisp code that's as imperative as Java. Whether this is good or bad is left up to the reader.

Use closures to create a simple object system. You'll see that you can quickly create systems ranging from Java-esque rigidity to smalltalk message passing to javascript prototypes pretty quickly. Then you can start making your own trade offs in object systems. This is something most people (including lisp programmers) don't do daily, and it gets you wondering about some very abstract things. The imposed structure of say, Python (or most other languages), limits you to thinking about "only" the problem domain. For most people (again, including lispers), narrowing the mental focus helps a lot.

CLisp, for example, is not a functional language in the sense of ML language or Haskell.

CLisp is a multi-paradigm language. You can use it in a OOP or a functional style. You can even use its OO features in a functional way and viceversa. E.g Objects are poor's people closures. [1]

[1] http://c2.com/cgi/wiki?ClosuresAndObjectsAreEquivalent

You could argue that it imposes a fanatically singular structure which is paradoxically what makes it so incredibly flexible.

One of my favorite things about Common Lisp is that it has gotos and stack unwinding to dynamically (at runtime) determined points:

http://www.lispworks.com/documentation/HyperSpec/Body/s_go.h...

http://clhs.lisp.se/Body/s_tagbod.htm

http://www.lispworks.com/documentation/HyperSpec/Body/s_thro...