**Exercise 1.3.31**

Let be the category of finite sets with bijections. We’ll define two functors . First, define . is the set of permutations of . For a bijection , define by .

Now, define . is the set of total orders on – for concreteness, let the elements of be relations in the sense of subsets of . Suppose is a bijection. Define by .

**Theorem**:
There is no natural transformation .

*Proof*:
Assume there were such a natural transformation .
Let .
And let be the swapping permutation and .
Then, we have a component and by naturality .
But, observe that:
which is some ordering, set .
Then,
which is clearly a different ordering than , a contradiction.

Thus, since and are the same size as sets, there is a bijection between them and we have in for each , but not *naturally*.
That is to say, and are not naturally isomorphic.
This is a counterexample to the incorrect “converse” one might be willing to draw from exercise 1.3.26.