"Your pronominative is rather in need of an antecedent, I'm afraid," Septimus answered without looking up from his book.
Thomasina just crossed her arms. "Septimus, really."
"Really, Thomasina. You could just have easily said 'what is that?' and I would be no more or less clear as to your meaning. When 'this' and 'that' might as well mean the same thing, what one is experiencing is a breakdown of the rules of grammar."
"Grammar is not the issue," Thomasina insisted, letting a little of her frustration into her voice.
"The issue," Septimus said, putting down his book, "is that I have no idea whatever in the world you might mean. What is what?"
"Us."
"You mean we. What are we. Although I should think we would be less of a what and more of a who."
"In any case."
"Nominative should do us fine, thank you. Context provides us with a referent, but I must admit that I am still quite in the dark as to your meaning. You are Thomasina Coverly, daughter of Lady Croom, and I am Septimus Hodge, your tutor."
Thomasina eyed him warily. "Is that all you are?"
"Of course not. If you believe what I am told by others, which I do not, I am a child of God in need of repentance. If you believe what I tell others, which I also do not believe, I am a well-qualified scholar in my own right."
"As opposed to in someone else's right?"
"Yours, Thomasina. Any greatness I achieve will be through you."
"Is that all you are to me?"
"I am your friend, if you will have me." He paused. "Are you of the opinion that I am omitting something?"
"I don't know. It just seems somewhat illicit, somehow. All--" she paused, then continued anyway, "--this."
Septimus considered. "It does. I'll give you that. Yet, we've done nothing wrong."
Thomasina nodded, thoughtfully. "No, there is that. We have not. I suppose we should have done something quite wrong were we to be illicit."
"You say that as if it were to be a virtue."
"You say that as if it were an accusation," she retorted.
"Isn't it? If we must do wrong to be illicit, then being illicit must be wrong. QED. It's a tautology."
"--which is no more than to say that it begs the question. Arguing from definition is always suspect. You taught me that."
Septimus considered. "I suppose I did. Should I not have?"
"On the contrary," she contradicted. "You did quite well. You have been a superlative tutor."
"I suppose I have."
"No supposition is required. You have been, I say it."
"Argument from authority is a fallacy as well, Thomasina."
"I'll walk you through the proof, then."
"Will you?"
"Only if we can do something quite wrong."
"We can do such a thing, but we may not."
"But we will anyway."
"Will we?"
"Mama refuses to let me to learn to waltz. Teach me to dance, Septimus."