I have long meditated on Shakespeare's rare reference to a cat as "a necessary cat". It seemed to me rather unbecoming for the graceful feline species. I have now changed my mind.
Yesterday, we witnessed the appointment of "Larry the Cat" to Number 10 Downing Street, having been rescued from Battersea Dogs (and Cats) Home. He is the Number 10 ratcatcher. This story started when on the main BBC TV News, during a report on politics, a large rat was clearly seen scuttling across the porch of the Prime Minister's residence. An outcry followed, with lots of quips about "rats" and "politicians". So Larry the cat was found and was appointed and his hunting instincts must justify his presence. He has not been chosen for his adorable looks, but for his working skills.
Shakespeare did not dislike cats. Being "necessary" becomes and sums up a working cat, and I now see that it is in praise of him, or her. A cat can make a real contribution to the welfare of the social human order. The poet was far less keen on "spaniels", which follow to heel, do no work, and represent in his works, flatterers at court (or in politics). They clearly nauseated him.