Doubt, uncertainty, or scepticism regarding the existence of a god or gods.
Doubt, uncertainty, or scepticism regarding any subject of dispute.
The view that absolute truth or ultimate certainty is unattainable, especially regarding knowledge not based on experience or perceivable phenomena.
The view that the existence of God or of all deities is unknown, unknowable, unproven, or unprovable.
Any of a range of concepts regarding spirituality and religion which do not include the idea of a deity in the form of a theistic god or gods.