"I believe in God" = theism
"I don't believe in god" = atheism (weak)
"I believe there is no god" = atheism (strong)
And:
"I believe we can never know either way" = agnosticism (strong)
"We don't know at the moment, but we might know in the future" = agnosticism (weak)
So you can be atheist and agnostic, or theist and agnostic:
"I don't believe in a god - you can't prove either way" = agnostic atheism
"I believe in God, but I think you can't prove He exists" = agnostic theism
"I don't believe in god" = atheism (weak)
"I believe there is no god" = atheism (strong)
And:
"I believe we can never know either way" = agnosticism (strong)
"We don't know at the moment, but we might know in the future" = agnosticism (weak)
So you can be atheist and agnostic, or theist and agnostic:
"I don't believe in a god - you can't prove either way" = agnostic atheism
"I believe in God, but I think you can't prove He exists" = agnostic theism
