When we ask whether something could have been different, we might be asking two radically distinct questions. The ambiguity lurks in ordinary language, generating philosophical puzzles that cut to the heart of essence and identity.

Consider: "The President could have been a different person." This seems obviously true—elections might have gone otherwise. But it also seems to say something about the actual President, the flesh-and-blood individual currently holding office. Could that person have failed to become President? These aren't the same question.

This distinction—between de dicto modality (concerning propositions) and de re modality (concerning objects themselves)—proves foundational for understanding what's genuinely possible. It reveals how modal claims connect to the essential natures of things and what makes objects the very individuals they are across different scenarios.

The Latin terminology marks a crucial scope distinction. De dicto ("of the saying") modality concerns what's necessary or possible for propositions considered as wholes. De re ("of the thing") modality concerns what's necessary or possible for particular objects themselves.

Consider: "Necessarily, the tallest person is tall." Read de dicto, this is trivially true—the proposition "the tallest person is tall" couldn't be false. But read de re, we're asking about whoever actually happens to be tallest: is that individual necessarily tall? Clearly not. Someone else might have been taller.

The ambiguity reflects different logical scopes. In the de dicto reading, the necessity operator governs the entire proposition. In the de re reading, we first fix on an object (the actual tallest person), then ask what's necessary for that very individual. The definite description falls outside the modal operator's scope.

This isn't mere linguistic tidiness. The distinction reveals that modal claims about objects carry metaphysical commitments beyond truth-conditions for propositions. When we attribute possibilities to things themselves, we presuppose that it makes sense to track those very things across different scenarios—that there's a fact about what they could have been.

Takeaway

Every modal claim hides a scope ambiguity: are we saying something is necessary about a description, or necessary about the particular thing that happens to satisfy it?

De re modality presupposes we can meaningfully speak of the same individual existing in different possible worlds. But what grounds such transworld identity? When we consider whether Socrates could have been a carpenter, we imagine Socrates—that very man—in a different situation. What makes that individual in the alternate scenario Socrates?

This generates the transworld identity problem. Possible worlds aren't connected by any causal or spatiotemporal relations. We can't trace a continuous path from Socrates here to Socrates there. So what criterion determines sameness of individual across worlds?

David Lewis proposed counterpart theory as an alternative. On his view, individuals exist in only one world—they don't literally recur across possibilities. Modal claims about objects are made true by counterparts: sufficiently similar individuals in other worlds. "Socrates could have been a carpenter" means some counterpart of Socrates is a carpenter in some possible world.

Counterpart theory has implications that strike some as counterintuitive. Your counterpart's properties aren't your properties—that individual isn't you. Critics argue this makes de re modality oddly indirect: we're not really asking what you could have been, but what someone relevantly like you is like. Defenders respond that this preserves modal discourse without mysterious transworld identity.

Takeaway

Asking what an object could have been requires explaining how the same object shows up in different possible scenarios—or else reconceiving de re modality as claims about similar individuals rather than identical ones.

De re necessities reveal essential properties—features an object couldn't lack in any possible world while still being that very object. If Socrates is necessarily human, humanity belongs to his essence. He couldn't have been a number or an abstract object; any world containing Socrates contains a human being.

This connects modal metaphysics to ancient questions about essence. For Aristotle, a thing's essence is what makes it the kind of thing it is. Contemporary essentialists translate this into modal terms: essential properties are those an object possesses in every world where it exists.

But which properties are essential? Origin essentialism holds that objects essentially originate as they actually do—you couldn't have been born from different parents. Kind essentialism claims objects essentially belong to their natural kinds—this gold ring is essentially gold. Sortal essentialism proposes objects essentially fall under their sortals—I'm essentially a person.

The debate matters because essential properties constrain identity. If certain properties are essential to you, then any possible individual lacking those properties simply isn't you—regardless of other similarities. Essence thus provides criteria for transworld identity: you exist in another possible world just in case something there has all your essential properties and appropriately connects to you.

Takeaway

What an object necessarily is reveals what it essentially is—those features without which it couldn't be that very thing at all.

The de re/de dicto distinction isn't philosophical hairsplitting—it marks fundamentally different questions. One concerns propositions and their truth-conditions. The other concerns objects themselves and what transformations they could survive.

De re modality commits us to views about transworld identity and essence. We must explain how individuals persist across possible scenarios, or else reinterpret modal claims as involving counterparts rather than strict identity.

Ultimately, asking what something could have been leads us to ask what it essentially is. Modal metaphysics and the theory of essence prove deeply intertwined—two perspectives on the fundamental nature of things.