# Rob Bensinger comments on Controllables and Observables, Revisited

• To get an intuition for morphisms, I tried listing out every frame that has a morphism going to a simple 2x2 frame

.

Are any of the following wrong? And, am I missing any?

Frames I think have a morphism going to :

Every frame that looks like a frame on this list (other than ), but with extra columns added — regardless of what’s in those columns. (As a special case, this includes the five frames corresponding to the other five ensurables that can be deduced from the matrix: , , , , . If has more than four elements, then there will be additional frames /​ additional ensurables beyond these seven.)

Every frame biextensionally equivalent to one of the frames on this list.

• is wrong. You can see it has Ensurables that does not have.

• You can also duplicate rows in , and then add columns, so you can get things like . There are infinitely many biextensional Cartesian frames over with morphism to , with arbitrarily large dimensions.