Blogs are an additional feature on PC and while everyone is free to comment on public blogs, they can only be created if you meet these criteria:
Become a Community Supporter of tier 2 or higher. (ie. donate at least $10)
Obtain at least 5000 posts.
Be selected by the staff.
Become a staff member.
As mentioned, there is a chance of being chosen specially by the staff for a blog. The staff may offer a blog to members who contribute actively to the community. If the staff believes you may have something worthwhile to contribute in a blog, there is a chance you will be selected to use the blogging feature.
It's the idea that we develop spiritually over time - so much, in fact, that the development can be called "evolution" in the same way that we have developed so much physically over time and we call that "evolution". In New Age, there is a theory that our physical and mental evolution has caused us to devolve spiritually and so we must find a way to evolve spiritually again. For example, atheism shows a major lack of spirituality but a height of mental development while monotheistic religions developed people spiritually (and physically) but left little room for mental development. As society changes, some things become lacking - even physicality is lacking in many people that seek to develop mentally and spiritually. If we do not pay attention to all forms of evolution, some forms may "devolve" - that is, we won't lose those things, but they will get stuck, frozen, and it'll be harder for us to develop them again.
It's Theosophy's interpretation of Evolution as described in detail in the book The Secret Doctrine. It has not just physical but also spiritual evolution described. My Exoreligion has en edited version of the Root Race theory, since I found many discrepancies in it, but for the most part the Root Race theory is deemed as correct as the backbone to evolution in my Exoreligion.