God, Spirit, is All. This is a fundamental point in divine metaphysics. All other truths of Christian Science relate to this one.
Why is there no matter? Why are man and the universe spiritual? Why are sin, sickness, and death unreal? Why is material existence illusory? Because Spirit, divine Love, is All and everywhere.
The logic is plain. And since Spirit's allness is scientific truth, it is demonstrable in the degree that we understand it. Demonstration need not be arduous or protracted when the spiritual premise—God's allness—is firmly established in consciousness without doubt or reservation.
