Wittgenstein wrote that the world was the totality of facts, not of things. But although facts have the nice solid ring about them that opposes them to such things as values or theories, they prove to be slippery items out of which to build anything. Facts seem to be shaped just like sentences: it is a fact that dogs bark and stones sink. It may also be a fact that children have rights or that sun and rain make rainbows. Modern thought has been sympathetic to a deflationist or minimalist view of the notion. On this account it is first pointed out that ‘it is a fact that p’ is the same as ‘it is true that p’, and that both reduce to simply: p. But if we want to know what makes it the case that p, it may be that there is no general answer. One kind of thing (dogs barking) makes it true that dogs bark, another kind of thing (stones sinking) makes it true that stones sink, and so on for any sentence we care to exhibit. This is not a rejection of the category of fact in favour of any kind of relativism or scepticism, since it is quite consistent with the view that for many examples of p we know whether p, there are no two views about p, and so on. But it is the denial that these assertions gain anything except perhaps rhetorical force by being couched in terms of facts. An attempt to build a more substantive theory of facts in general needs to address questions such as whether there are negative as well as positive facts, general facts as well as particular ones, facts about values as well as facts about the physical world, dispositional and categorical facts, and so on. It will also need principles for counting facts: is the fact that I have a sister one fact or two (two people were her parents, and the same two people were my parents). The last well-known systematic philosophy of facts was the Tractatus Logico-Philosophicus of Wittgenstein, which depended heavily on a conception of atomic or basic facts, conceived as logically simple, independent structures in a logical space. But Wittgenstein repudiated the metaphysic in his later work. See also truthmaker principle.