 Scenarios clearly have much in common with centered worlds. Indeed, it may be possible to simply identify scenarios with centered worlds. (Chalmers is cautious about this, noting reasons that some might reject this identification, but makes use of it for some purposes.) If scenarios are thought of as centered worlds, then the idea that narrow content is a function from scenarios to truth values is obviously a close cousin of the idea that narrow contents are diagonal propositions, which can also be thought of as functions from centered worlds to truth values. The differences between the two accounts should not be underestimated, however. An immediate formal difference is that narrow contents on Chalmers’ approach are defined over a larger class of centered worlds than are diagonal propositions. On the diagonal approach, the centered worlds with respect to which a thought is evaluated must include a token of that very thought at the center, while this is not the case on the approach we are now considering. Another substantive difference between the two views is that they lead to very different strategies for determining narrow contents, as will emerge in sections 5.1 and 5.4.