 “All propositions are of equal value” (TLP 6.4)—that could also be the fundamental thought of the book. For it employs a measure of the value of propositions that is done by logic and the notion of limits. It is here, however, with the constraints on the value of propositions, that the tension in the Tractatus is most strongly felt. It becomes clear that the notions used by the Tractatus—the logical-philosophical notions—do not belong to the world and hence cannot be used to express anything meaningful. Since language, thought, and the world, are all isomorphic, any attempt to say in logic (i.e., in language) “this and this there is in the world, that there is not” is doomed to be a failure, since it would mean that logic has got outside the limits of the world, i.e. of itself. That is to say, the Tractatus has gone over its own limits, and stands in danger of being nonsensical.