De dicto and de re

De dicto and de re are two phrases used to mark important distinctions in intensional statements, associated with the intentional operators in many such statements. The distinctions are most recognized in philosophy of language and metaphysics.

The literal translation of the phrase de dicto is "of (the) word", whereas de re translates to "of (the) thing". The original meaning of the Latin locutions is useful for understanding the living meaning of the phrases, in the distinctions they mark. The distinction is best understood by examples of intentional contexts of which we will consider three: a context of thought, a context of desire, and a context of modality.

Context of thought
There are two possible interpretations of the sentence “Peter believes someone is out to get him”. On one interpretation, ‘someone’ is unspecific and Peter suffers a general paranoia; he believes that it is true that a person is out to get him, but does not necessarily have any beliefs about whom this person may be. What Peter believes is that the predicate ‘is out to get Peter’ is satisfied. This is the de dicto interpretation.

On the de re interpretation, ‘someone’ is specific, picking out some particular individual. There is some person Peter has in mind, and Peter believes that person is out to get him.

In the context of thought, the distinction helps us explain how people can hold seemingly self-contradicting beliefs. Say Lois Lane believes Clark Kent is weaker than Superman. Since Clark Kent IS Superman, taken de re, Lois’s belief is untenable; the names ‘Clark Kent’ and ‘Superman’ pick out an individual in the world, and a person (or super-person) cannot be stronger than himself. Understood de dicto, however, this may be a perfectly reasonable belief, since Lois is not aware that Clark and Superman are one and the same.

Context of desire
Consider the sentence "Jana wants to marry the fattest man in Utah". There are two ways to interpret this sentence. One interpretation is that Jana (due to some strange fetish perhaps) wants to marry the fattest man in Utah, whomever he might be. On this interpretation, what the statement tells us is that Jana has a certain unspecific desire; what she desires is that a certain situation should obtain, namely, Jana's marrying the fattest man in Utah. The desire is directed at that situation, regardless of how it is to be achieved. The other interpretation is that Jana wants to marry a certain man, who in fact happens to be the fattest man in Utah. Her desire is for that man, and she desires herself to marry him. Again, the first interpretation, "Jana desires that she marry the fattest man in Utah", is the de dicto interpretation. The second interpretation, "Of the fattest man in Utah, Jana desires that she marry him", is the  de re interpretation.

Another way to understand the distinction is to ask what Jana would want if the man who was the fattest man in Utah at the time the original statement was made were to lose weight, such that he was no longer the fattest man in Utah. If she continued to want to marry that man – and, importantly, perceived this as representing no change in her desires – then she could be taken to have meant the original statement in a de re sense. If she no longer wanted to marry that man but instead wanted to marry the new fattest man in Utah, and saw this as a continuation of her earlier desire, then she meant the original statement in a de dicto sense.

Context of modality
Take the sentence "The number of planets in our solar system is necessarily even". Again, there are two interpretations. The first interpretation is that things could not have gone differently, with the number of planets in our solar system turning out to be odd. Intuitively, this claim is false. Presumably, things could have gone differently, so that our solar system ended up with, for example, only seven planets. The second interpretation is that things could not have gone differently, with the number eight turning out to be even. Intuitively, this claim is true. Of all the ways the world could have turned out, presumably there are no possibilities wherein the number eight is odd. Eight's evenness seems to be a necessary fact. The first interpretation, which seems to yield a false statement, is the de dicto interpretation. The second interpretation, which seems to yield a true statement, is the de re interpretation.

Another example: "The President of the USA in 2000 could not have been Al Gore". This claim seems false on a de dicto reading. Presumably, things could have gone differently, with Gore winning the election. But it looks more plausible on a de re reading. After all, we might skeptically wonder of George W. Bush, whether he could have been Al Gore. Indeed, assuming that being George Bush is an essential feature of GB and that this feature is incompatible with being Al Gore, a de re reading of the statement is true.

Representing de dicto and de re in modal logic
In modal logic de dicto and de re are represented by putting the quantifier after the modality for de dicto and before the modality for de re. For example: