Category Axioms are Self-Dual/Object Category Theory

Theorem
Let $\mathrm {CT}$ be the collection of seven axioms on Characterization of Metacategory via Equations.

Then:


 * $\mathrm {CT} = \mathrm {CT}^*$

where $\mathrm {CT}^*$ consists of the dual statements of those in $\mathrm{CT}$.

Proof
The seven axioms are:

Their duals are:

It is seen that only names of the bound variables $f, g$ and $h$ have been changed at some places.

Therefore, we conclude:


 * $\mathrm {CT}^* = \mathrm {CT}$