These are some of the most frustrating concepts to engage in dialog over with an atheist. It has been my experience that in the majority of cases they will defend some form of a naturalistic explanation for all things, deterministic or otherwise, while simultaneously arguing that their beliefs, defenses, and emotional responses to the discussion hold true meaning. This is of course untenable and somewhat ironic.
What inevitably follows is a discussion of what makes something meaningful. Of course the proposition that we can assign ultimate meaning to something by fabricating it is also untenable and gives rise to further irony. It is rare to find an atheist that is willing to admit that their worldview holds no ultimate meaning, and that as a result everything they "know" and defend is illusory. It does happen, but rarely. It is simply not congruent with our experience of the evidence that meaning does not exist, and yet without an outside source providing the framework for that meaning to flow from it is problematic to defend its existence without circular reasoning.