Maarten Maartensz:    Philosophical Dictionary | Filosofisch Woordenboek                      

 D - Description


Description: (In a logical Russellian sense): A formula that corresponds to "there is precisely one thing F that is  also G". In logical formalism: (Ex)(y)(F(x) & (y)(Fy --> x=y) & Gx).

An example, also due to Bertrand Russell is: The present King of France is bald. Since France has no King, this is not true.

Note that there are two ways in which
(Ex)(y)(F(x) & (y)(Fy --> x=y) & Gx) is not true. The first simply denies the whole statement, thus: ~(Ex)(y)(F(x) & (y)(Fy --> x=y) & Gx), and the second does not deny the whole statement, but only the part Gy. thus: (Ex)(y)(F(x) & (y)(Fy --> x=y) & ~Gx).



See also:


Russell & Whitehead, any decent introduction to mathematical logic.

 Original: Jul 6, 2016                                                Last edited: Jul 6, 2016