First-order aboutness theory

We seem to have a good grasp of how the subject matters of truth-functional composites depends on their components: it’s simply fusion (Hawke in Australas J Philos 96:697–723, 2018, Fine in Philos Studies 177:129–171, 2020, Plebani and Spolaore in Philos Q 71:605–622, 2021, Plebani and Spolaore in Philos Stud 181:247–265, 2021, Berto in Topics of Thought, Oxford University Press, Oxford, 2022). But what relation should the subject matter of subsentential components bear to the subject matter of the sentences they feature in, and what to say about the quantified sentences of first-order predicate logic? Given how well we seem to understand sentential subject matter in the context of propositional logic, I propose a reduction of the subject matter of subsentential components and of quantified sentences to the subject matter of quantifier-free sentences. I argue that the view squares with the Fregean intuitions that gave rise to the construction of first-order logic as we know it today, motivating its adequacy as a theory of subject matter for first-order languages. I then show that this first-order aboutness theory has predictive and explanatory power, leading us to accept a modified version of Yablo’s (Aboutness, Princeton University Press, Princeton, 2014) principle of immanent closure, as well as a new conception of arbitrary objects/reference. Finally, I propose some potential developments and restrictions.