From: John Owen in Don Whitney's How Can I Be Sure I'm A Christian? These are the subheadings within the chapter, and are worthwhile in themselves. For more, get the book!
ONLY THOSE WHO ARE SPIRITUALLY MINDED ARE CHRISTIANS.
YOU ARE SPIRITUALLY MINDED WHEN YOU THINK ABOUT THE THINGS OF GOD SPONTANEOUSLY AND WITHOUT EXTERNAL CAUSES.
YOU ARE SPIRITUALLY MINDED WHEN YOU THINK ABOUT THE THINGS OF GOD MORE THAN ANYTHING ELSE.
YOU ARE SPIRITUALLY MINDED IF YOU THINK ABOUT THE THINGS OF GOD WITH MORE DELIGHT AND ENJOYMENT THAN ANYTHING ELSE.
YOU ARE NOT SPIRITUALLY MINDED IF "GOD IS NOT IN ALL YOUR THOUGHTS."