The definition of inclusivism I have seen is that while Christ is soteriologically necessary for salvation, he is not epistemologically necessary. Ie, one does not have to know who he is, or hear the Gospel, because, Inclus believe, the Holy Spirit is working on everyone (prevenient grace gone mad) even through their religion, as opposed to just those to whom the gospel is being offered.
For those that know, Lewis' Till We Have Faces, and the end of Last Battle re Emeth set the case. Yx said "we are talking about Inclusivism that was made popular by Karl Rahner (a Roman Catholic theologian), CS Lewis, Clark Pinnock". Notice the first tow are not Evangelicals, and the latter got his ideas from the former. Oh, and Process Theology