De dicto and de re
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De dicto and de re are two phrases used to mark important distinctions in intensional statements, associated with the intensional 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 intensional contexts of which we will consider three: a context of thought, a context of desire, and a context of modality.
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[edit] Context of thought
Take the sentence "Peter regards everyone else as out to get him". There are two ways to interpret the sentence. One interpretation has Peter thinking in terms of a general paranoia; on this interpretation, the statement tells us something that Peter thinks, and what he thinks is the following: Everyone else is out to get me. We could also put this by saying, "Peter regards the following as true: that everyone else is out to get him." This is the de dicto interpretation. The second interpretation has Peter thinking in terms of an individualized paranoia; on this interpretation, the statement does not tell us about any particular thought of Peter's at all, but tells us, rather, of an attitude he holds towards a great many individuals. For every other person in the world, on this interpretation, Peter regards (thinks of) that person as being out to get him. (If true, this means Peter knows everyone else individually, and has his suspicions of each one of us.) This is the de re interpretation.
[edit] 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, whoever 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.
[edit] Context of modality
Take the sentence "The number of planets in our solar system is necessarily odd". 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 even. Intuitively, this claim is false. Presumably, things could have gone differently, so that our solar system ended up with, for example, only six planets. The second interpretation is that things could not have gone differently, with the number nine 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 nine is even. Nine's oddness 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 2004 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 Presidency. 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.
[edit] 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:
| De dicto: |  |
Necessarily, some x is such that A |
| De re: |  |
Some x is such that necessarily A |
