Although the emphasis in the previous two chapters was on the form of expressions (in a sense showing how statements as units of the logical system are meaningful only in speech-contexts), there were many occasions where it was clear that Avicenna considered the constituents of those statements primarily to be some kind of mental objects – that statements are acts whereby we perforce can only associate one idea in our minds with another: it is these ideas that constitute our universe of discourse. This immediately gives rise to three main questions. What exactly are those mental constituents – the subjects and predicates in our universe of discourse? What exactly is the nature of that reality – the order of things – which our statements purport to be about? And in what sense can we claim that these two dimensions or registers correspond with one another? Indeed, given the distinction, we may seriously question whether Avicenna can provide us with an explanation how we can ever be sure that our claims of knowledge about the world – even if fine-tuned by our logical tools – can be shown to reflect its reality: how what we can agree to be a true statement can actually be shown to be true! We will leave this last question to the last chapter. But first, we have to look more closely at what those mental objects are – the Bs and As or x’s and Fs that were the material for the different rules discussed earlier. What are they, exactly?