I strongly agree. We see a lot of definitions of functional bandied about, often conflating functional with Haskell or with Scala. Those definitions seem to i

I strongly agree. We see a lot of definitions of functional bandied about, often conflating functional with Haskell or with Scala. Those definitions seem to ignore the history of functional programming, including Lisp, as qsymmachus noted. So that's silly. And conversely, one sees a lot of definitions of OO that appear to mean "Java" or "C++". Again, nonsensical when one considers Self, or to a lesser degree Smalltalk. I do like your conception wherein a language is function to the degree to which it prefers functions as its favourite tool for solving problems, and/or OO to the degree to which it prefers objects as its favourite tool. Regarding encapsulation as your particular example, OO is clearly fairly obsessed with encapsulation, being almost the definition of an object: a bundle of encapsulated state with the externally-facing behaviour that that object affords. I think that many functional communities/practitioners see this as a much less urgent issue, often going so far as to make no active effort toward encapsulation at all (i.e. not everyone bothers with the lexical-scopes-and-closures solution). Thus we get ideas like "smart functions, dumb data", an idea which makes no sense in OO land.