LSP came out of Liskov's work on CLU (amongst other things). CLU didn't have inheritance, though it did have have 'interface specifications'. LSP is most proper

LSP came out of Liskov's work on CLU (amongst other things). CLU didn't have inheritance, though it did have have 'interface specifications'. LSP is most properly thought of as pertaining to interfaces rather than inheritance. LSP as most people seem to currently conceive it is coloured by their experience with languages like C++, where inheritance and polymorphism are welded to one another. Same goes for the likes of Java, albeit to a lesser extent. In the case of languages like that, LSP also needs to deal with the subclass/superclass relationship, and that has over time overshadowed its most important aspect: substitutability of implementations.