# [FOM] The Irrelevance of definite descriptions in the Slingshot Argument?

A.S.Virdi@lse.ac.uk A.S.Virdi at lse.ac.uk
Thu Sep 28 07:57:02 EDT 2006

```
Dear FOMers,

Can anyone think of any significant mathematical difference between the
following two arguments?

1. s                                                    Premise
2. {x: x = d & s} = {x: x = d}  From 1., given substitution salva
veritate of logical equivalents
3. {x: x = d & t} = {x: x = d}  From 2., given substitution salva
veritate of co-referring terms
4. t                            From 3., given substitution salva
veritate of logical equivalents

And (with i is the iota/definite-description operator)

1. s                                                    Premise
2. ix(x = d & s) = ix(x = d)    From 1., given substitution salva
veritate of logical equivalents
3. ix(x = d & t) = ix(x = d)    From 2., given substitution salva
veritate of co-referring terms
4. t                            From 3., given substitution salva
veritate of logical equivalents

Both arguments seem valid (don't they?). So why has there been much