This voluntary cooperative model of OO gives the screaming horrors to Smalltalkers and other purists, but it leaves a lot of space for us to work in.

Most versions of Smalltalk do not actually have any notions of public/private/protected in the way Java/C++ does. Instead Smalltalk's notion of private methods is very similar to perl's, "If you weren't invited, don't come in". Smalltalk has things called method categories, which in the language are really are nothing more than syntactic sugar, but when you combine it with the Smalltalk environment, in particular the Smalltalk code browser, you have another layer of organization between the class-level and method-level. Typically Smalltalk programmers will put all their private methods into the "Private" category. Some Smalltalk implementations will complain (the equivalent of warn) when you call a method that is prefixed with an _ from outside of your class, but none (at least that I know of) will actually enforce this and not let you compile your code. Here is a link that goes into more detail if you are intetested.