That's great but I don't think that you have gone far enough here.
What you then need to point out is that there is no good reason to believe that the sun will come up tomorrow, as what is true of the past is not necessarily true of the future.
We're not far away from Christmas, so perhaps an example will serve as an illustration of what I am attempting to convey here. Think of a turkey who is greeted every morning with a bucket of grain from a friendly farmer. When this happens repetitively, the turkey would probably conclude that things are going to carry on that way.
Until the morning of the 24th December.
After that, see if you can find a pool or snooker table and then play a frame of it with them (remember that they should keep their head down and gently follow through a little when playing a shot).
Then ask them to show you the actual power, force or whatever it is that causes the second ball to move on impact whenever a shot is played. I think you may find that they are unable to do so.
Staying with the Christmas theme that I have introduced, you could then invite them to say what they would like as a present. At the same time, inform them that you will be perfectly happy to buy them anything that they want, absolutely anything, no matter how expensive it is, provided that beforehand they do a bit of introspection in order to locate the precise whereabouts of the 'I' which wants the present.
You should find that they will fail with this one too.
Of course, I am being mischievous.
But if, when they were older, they opted to do an A Level in Religious Studies, they would encounter all these ideas, as they almost always feature on the syllabus. And that's because sixth-formers have to study David Hume (on miracles, the existence of God, induction, causation*, and the nature of the self**).
Hume isn't radical or sceptical enough for Buddhists, though. So if they were studying that faith and Hume (which some actually do) you would eventually have to grips with the paradoxical nature of truth, maybe by studying the idea of the four-cornered negation in Nagarjuna's Mūlamadhyamakakārikā ('S is neither P, nor not-P, not both P and not-P, nor neither P nor not-P) or attempting to solve some koans. A good one to start with might be, “What is your original face, the face you had before you were born?”
* ‘Our idea, therefore, of necessity and causation arises entirely from the uniformity observable in the operations of nature, where similar objects are constantly conjoined together, and the mind is determined by custom to infer the one from the appearance of the other…. Beyond the constant conjunction of similar objects, and the consequent inference from one to the other, we have no notion of any necessity or connexion.'
** ''For my part, when I enter most intimately into what I call myself, I always stumble on some particular perception or other, of heat or cold, light or shade, love or hatred, pain or pleasure. I never can catch myself at any time without a perception, and never can observe anything but the perception.'
