The distinction is between a thing in relation to other things and for us and a thing in itself. To the extent that water cannot wet, it is not water. To the extent that fire cannot burn, it is not fire. Yet precisely for not burning itself, fire is fire; and for not wetting itself, water is water. X is not X, therefore it is X. For precisely in its act of burning firewood, fire does not burn itself; and in not burning itself, it burns firewood. It burns in relation to something else, but in-itself (in relation to itself) it does not burn.