“Science as a system of statements is always an object of discussion. Statements are to be compared with statements, and not with 'experience', or with 'the world', or with something else. All that meaningless doubling belongs to more or less subtle metaphysics and as such must be rejected. Every new statement is to be confronted with existing ones, already brought to a state of harmony between themselves. A statement will be considered correct if it can be joined to them.”