"Everything we do is for the purpose of altering consciousness." I very much respect Sam Harris for taking the consciousness problem seriously. It poses a real problem to (his) atheism, and he, obviously, rejects the substance dualism, which would logically lead to a religious view on us. However, without a conscious soul, meaning itself loses meaning. What's the ontological support for meaning to rise on? One thing…
Only for competitive reasons. To get a stable foothold, Christianity had to either do away with the rampant spiritualism of the largely shamanistic religions it replaced, or in some cases had to embrace and extend them. This is and was a purely strategic consideration.
> It poses a real problem to (his) atheism, and he, obviously, rejects the substance dualism, which would logically lead to a religious view on us.
One of his personal core issues is to "rescue" spiritual experiences and bring them over into a secular world. It is not necessarily a concern of atheism per se. For him, as for most atheists, there is not really a "consciousness problem" comparable to what a religious person might identify. As an atheist myself, there is nothing inherently problematic about consciousness, or intelligence, or feelings.
> However, without a conscious soul, meaning itself loses meaning. What's the ontological support for meaning to rise on?
I think most atheists, myself included, as well as many religious people would agree with you that the mind gives rise to meaning. However, I have no idea what you mean by ontological support? Are you asserting that without an overriding supernatural meaning-giver the mind cannot form a world view? Or that a mind capable of categorizing the world meaningfully cannot arise without supernatural influence?