Well it all depends on how you define religion. Religion's not a concrete word.
Merriam Webster Online Dictionary:
- a : the state of a religious <a nun in her 20th year of religion>
b (1) : the service and worship of God or the supernatural. (2) : commitment or devotion to religious faith or observance - a personal set or institutionalized system of religious attitudes, beliefs, and practices
- archaic : scrupulous conformity : CONSCIENTIOUSNESS
- a cause, principle, or system of beliefs held to with ardor and faith
The first three seem to lean more on our modern, more well-known definition of religion, but 4 is a bit iffy. Simpleism (if you can even put a name on it) could then be called a religion because it would then be a specific way of living life, something which you believe in and you have faith in, and be passionate about. You don't necessarily have to worship a higher figure.
Oh, and I Wikipedia'd it.
QUOTE
Members of the Religious Society of Friends (Quakers) practice the Testimony of Simplicity, which is the simplifying of one's life in order to focus on things that are most important and disregard or avoid things that are least important.
http://en.wikipedia.org/wiki/Simplicity