MathOverflow will be down for maintenance for approximately 3 hours, starting Monday evening (06/24/2013) at approximately 9:00 PM Eastern time (UTC-4).
show/hide this revision's text 3 deleted 8 characters in body

In their book "Theory of sets" Bourbaki suggested a general theory of isomorphism.

It seems that the Bourbaki theory can be greatly simplified if we allow only one principal base set.

(See also http://www.tau.ac.il/~corry/publications/articles/pdf/bourbaki-structures.pdf )

The example of an untransportable relation (i.e. formula) in the book involves 2 principal base sets.

Are there examples of untrasportable formulas when we allow only one principal base set?
show/hide this revision's text 2 added tag "Bourbaki"
show/hide this revision's text 1

Bourbaki theory of isomorphism, examples of untransportable formulas

In their book "Theory of sets" Bourbaki suggested a general theory of isomorphism.

It seems that the Bourbaki theory can be greatly simplified if we allow only one principal base set. The example of an untransportable relation (i.e. formula) in the book involves 2 principal base sets.

Are there examples of untrasportable formulas when we allow only one principal base set?