According to the theory, propositions can "picture" the world as being a certain way, and thus accurately represent it either truly or falsely. If someone thinks the proposition, "There is a tree in the yard," then that proposition accurately pictures the world if and only if there is a tree in the yard. One aspect of pictures which Wittgenstein finds particularly illuminating in comparison with language is the fact that we can directly see in the picture what situation it depicts without knowing if the situation actually obtains. This allows Wittgenstein to explain how false propositions can have meaning (a problem which Russell struggled with for many years): just as we can see directly from the picture the situation which it depicts without knowing if it in fact obtains, analogously, when we understand a proposition we grasp its truth conditions or its sense, that is, we know what the world must be like if it is true, without knowing if it is in fact true (TLP 4.024, 4.431).