No single creature honest mind can say they know the ABSOLUTE truth about anything, so it still goes from person to person. Atheism just denies the existence of a "higher power" entity in the most obvious senses. Most "ism"s conform to concrete beliefs, but things get fuzzy on a person to person basis.
I would like to believe in outer influence, but it is far too understandable that we are organic, and are thusly bound by memory alone. WE ARE MEMORY. That's it. Theism cannot change that. If you take a person and mess with their mind, from an injury or some other trauma, they might be a similar person, but it's our memories that dictate all aspects of our existence as we know it. Same as in death. Take a PC, with all of its memories and tools and plug-ins. Then smash it. You might be able to turn it on again, but it isn't the same. It may very well be beyond reach of communication. Regardless of what you believe, a similar instance DOES happen to the living just before death. Most ALL deaths (meaning the actual ceasing of both voluntary and involuntary thought/motion/processes) are "caused" by suffocation of the brain. Heart stops, brain suffocates. There's nothing that can prevent that. Even the beheaded have as many motor skills as their muscles and nerves allow before their minds finally cease in motion, then in charges, then the cortex loses all power. Have you ever damaged a power supply? A similar thing occurs. The motherboard tries, but there's not enough to get the processes going, and it gives up. Like unplugging a PC during an important process, you may lose valuable data, or even destroy the core system. And a virus can easily destroy the infrastructure and cause insanity. The persona is lost.
Is there a soul in there somewhere? Perhaps, but let's take the physical sense into account. The memories are all we have, aside from what those memories make our body do. Maybe they could be a substitute for a soul. The soul, as told be science and theory. We could be artistic as well, as memories allow us anything in terms of imagination, and say that souls are the untouchable, the sole property of ourselves and whatever we pledge them too. That could very well be a plausible statement, because one could hold that as truth to them.