'By the same token you wouldn't be using a stick by six p.m. because you'd be only, er, 52,' said Teppic, scribbling furiously. 'In fact you wouldn't really be looking at any kind of walking aid until at least half past nine, I think. That's on the assumption that the entire lifespan takes place over one day which is, I believe I have already pointed out, ridiculous. I'm sorry, it's basically okay, but it doesn't work.'
'Well,' said the Sphinx, but irritably this time, 'I don't see what I can do about it. I haven't got any more. It's the only one I've ever needed.'
'You just need to alter it a bit, that's all.'
'How do you mean?'
'Just make it a bit more realistic.'
'Hmm.' The Sphinx scratched its mane with a claw.
'Okay,' it said doubtfully. 'I suppose I could ask: What is it that walks on four legs'
'Metaphorically speaking,' said Teppic.
'Four legs, metaphorically speaking,' the Sphinx agreed, 'for about-'
'Twenty minutes, I think we agreed.'
'Okay, fine, twenty minutes in the morning, on two legs'
'But I think calling it in “the morning” is stretching it a bit,' said Teppic. 'It's just after midnight. I mean, technically it's the morning, but in a very real sense it's still last night, what do you think?'
A look of glazed panic crossed the Sphinx's face.
'What do you think?' it managed.
'Let's just see where we've got to, shall we? What, metaphorically speaking, walks on four legs just after midnight, on two legs for most of the day-'
'Barring accidents,' said the Sphinx, pathetically eager to show that it was making a contribution.
'Fine, on two legs barring accidents, until at least suppertime, when it walks with three legs-'
'I've known people use two walking sticks,' said the Sphinx helpfully.
'Okay. How about: when it continues to walk on two legs or with any prosthetic aids of its choice?'
The Sphinx gave this some consideration.
'Ye-ess,' it said gravely. 'That seems to fit all eventualities.'
'Well?' said Teppic.
'Well what?' said the Sphinx.
'Well, what's the answer?'
The Sphinx gave him a stony look, and then showed its fangs.
'Oh no,' it said. 'You don't catch me out like that. You think I'm stupid? You've got to tell me the answer.'
'Oh, blow,' said Teppic.
'Thought you had me there, didn't you?' said the Sphinx.
'Sorry.'
'You thought you could get me all confused, did you?'