For a
Christian to refer to themself as "more spiritual than religious" implies relative deprecation of rules, rituals, and tradition while preferring an intimate relationship with God and/or talking to Him as one's best friend. Their basis for this belief is that
Jesus Christ came to free man from those rules, rituals, and traditions, giving them the ability to "walk in the spirit" thus maintaining a "Christian" lifestyle through that one-to-one relationship with God. Some excellent resources that further explain the "spiritual Christian" are found in the
Bible,
Gospel of John 4:24 for example, and in the works of
Watchman Nee.
[2] Nee probes deeply into the building blocks of mankind and derives that we are Spirit, Body and Soul.