 The modal first-order language is built in a straightforward way: simply take the classical  first-order language,  with its universal \((\forall)\) and existential \((\exists)\) operators indicating quantification over objects, and add the two basic modal alethic operators, necessity \((\Box)\) and possibility \((\Diamond)\). The resulting language turns out to be very expressive, allowing us to distinguish between the de dicto and the de re readings of natural language sentences (a contrast that can be traced back to Aristotle; see Nortmann 2002). For example, assume that an individual f has exactly 3 sisters, and consider the sentence “the number of sisters of f is necessarily greater than 2”. The claim can be understood in two different ways. Under a de dicto interpretation, it states that the number of sisters that f has is necessarily greater than 2, but this is clearly questionable: under different circumstances, f might have had either more or else fewer sisters. However, under a de re interpretation, the claim states that the number of sisters that f has, the number 3, is necessarily greater than 2: this is definitely true, at least when restricting ourselves to the standard understanding of numbers.