If, as we are told by Atheists/Naturalists/Materialists, unguided evolution and unguided natural processes are the only causes of our existence and our thoughts, then why should we even believe that our thoughts about the world are accurate, and why should assume that our reasoning is sound?
I'm not sure why there would be an assumption that "unguided natural processes" should not be capable of producing reasoning, self-aware beings. Where is that rule written? That's just it; there are no rules written. It's a marvelous universe, with infinitely more questions than answers.
As far as "unguided" evolution, we must clarify that we mean 'unguided by a supernatural intelligent force,' since the principle of natural selection in conjunction with natural physical laws serves to guide living things into adaptable forms for long-term survival and replication.
An observer may see a river and reason that the cohesion and constant course of the water particles demands an intelligence at work, when in reality the very nature of water and the surface over which it flows determines its pattern.