“Inclusion” is a word used widely, but what do we mean by this? How does it happen? Who makes it happen? Given that we are not inclusive now, it has to be a futuristic concept – something we are striving for. If we had achieved it we would be talking about inclusiveness, and we wouldn’t be writing policies and advocating for it.
A conference paper discusses what we mean by inclusion and it illustrates why it is hard to achieve. The difference between inclusion and inclusiveness is more than semantics. They have different perspectives and ask different questions. Inclusion relies on one group looking at another group and inviting them in. It maintains a language of separation, for example, accessible, disabled, elderly and design-for-all. Inclusiveness looks at everyone equally and 
supports a whole population approach. Economic arguments and solutions are viewed differently. Inclusiveness is not a contest of rights and not one group giving something to others. All costs and benefits are measured from this perspective.
The key concepts are captured in a PDF of a PowerPoint presentation and the full paper is titled, Turning Back Time for Today as Well as Tomorrow available on ResearchGate.
Mismatch: How Inclusion Shapes Design by Kat Holmes discusses similar concepts.