Cornelius Appin has done the impossible: he has trained a regular cat to talk and make full use of human speech. While his deed is, in fact, quite amazing, it is very hard for those who surround Mr. Appin at the gathering in Lady Blemley's estate to feel any amazement. Appin's personality conflicts greatly with his great intellect. Given that he is not charming or exciting, the snobby guests are unimpressed and take the experiment as a joke.
He was neither a wit nor a croquet champion, a hypnotic force nor a begetter of amateur theatricals. Neither did his exterior suggest the sort of man in whom women are willing to pardon a generous measure of mental deficiency.
Appin overuses words, takes himself extremely seriously, and does not seem to recognize the awkward nature of his project. He has no social filters, and this prompts him to talk a lot about himself and his success with the cat. What this suggests is that he is proud of himself to a point of superiority. The evidence of this shows each time he has to explain his project. At one point, he adopts a patronizing attitude, talking about his experiment to a guest as if she were a student.
"My dear Miss Resker," said the wonder-worker patiently, "one teaches little children and savages and backward adults in that piecemeal fashion; when one has once solved the problem of making a beginning with an animal of highly developed intelligence one has no need for those halting methods."
The key problem with Appin is also that he cannot be taken seriously by this group of people. They are typical, upper class, aloof individuals who are so self-absorbed that they cannot fathom giving Appin their full attention.
Nevertheless, it is the cat who steals the show, shocking everyone not only because of his ability to speak, but also because of the knowledge that he has acquired in all of his daily comings and goings.
Tobermory, prancing around the household and entering every room like cats often do, has collected incendiary intelligence about many of the guests of the estate. He could blackmail them all, for all they know, since he has heard their most private conversations and has no qualms about saying everything he knows.
In all, the amazing Tobermory project has left Cornelius Appin quite proud of his final product, and his behavior shows that he is a very proud man who wishes to be seen respectfully by the not-so-respectful "set" of fashionable guests at the estate of Lady Blemley.