It is difficult to say at what age, precisely, we should pass from the first to the second part of the Trivium. Generally speaking, the answer is: so soon as the pupil shows himself disposed to pertness and interminable argument. For as, in the first part, the master faculties are Observation and Memory, so, in the second, the master faculty is the Discursive Reason. In the first, the exercise to which the rest of the material was, as it were, keyed, was the Latin grammar; in the second, the key- exercise will be Formal Logic. It is here that our curriculum shows its first sharp divergence from modern standards. The disrepute into which Formal Logic has fallen is entirely unjustified; and its neglect is the root cause of nearly all those disquieting symptoms which we have noted in the modern intellectual constitution. Logic has been discredited, partly because we have come to suppose that we are conditioned almost entirely by the intuitive and the unconscious. There is no time to argue whether this is true; I will simply observe that to neglect the proper training of the reason is the best possible way to make it true. Another cause for the disfavor into which Logic has fallen is the belief that it is entirely based upon universal assumptions that are either unprovable or tautological. This is not true. Not all universal propositions are of this kind. But even if they were, it would make no difference, since every syllogism whose major premise is in the form "All A is B" can be recast in hypothetical form. Logic is the art of arguing correctly: "If A, then B." The method is not invalidated by the hypothetical nature of A. Indeed, the practical utility of Formal Logic today lies not so much in the establishment of positive conclusions as in the prompt detection and exposure of invalid inference.
Until recently, I was wondering how I would know that my oldest child was beginning to transition from the "Poll-Parrot" stage to the "Pert" stage, which would let me know that I needed to start transitioning my Trivium-influenced instruction of her from Grammar to Dialectic. She seemed quite rooted and content in the Grammar stage, and it seemed that it might be another year or more before I had anything to say on the subject of the second year of the Trivium, that is, the Dialectic.
Then a few weeks ago, dd8 started showing an ability to analyze that she had previously lacked. On an embarrassing topic, of course. She looked up from her DK Big Book of Knowledge page on human reproduction and said, "Mommy, I know why males have to be bigger than females. It's so that they can...", and her childish guess at the mechanics of human intercourse followed. I responded with one of those honest-answers-to-her-question-without-telling-her-more-than-she-needs-to-know-at-her-age and then deflected her to a discussion of nonhuman mammalian intercourse for my own nerves' sake. So sue me for being a cowardly procrastinator. Deflection is a valuable tool, and she is only eight years old. Can she just apply her new-found analytical abilities to doing her laundry properly now?
As for the pertness, that's starting to show up, too. Last week, when I told her to set plates on the table for a meal, she asked "How many?" I responded, "One for each person." She then got a little smart-alecky look on her face and asked, "One for each person in the family or one for each person in all of [our city]?" The Besserwisserchen*.
I have some logic workbooks, and I plan to cover formal logic with her. But I will wait until she is fully ready for the Dialectic stage. We still have lots to cover while she is in the last part of the Grammar stage.
*German for a little smartypants.