Gadolhadorah,
“Your reading of my post was that the Tana in the Mishna “made up” the 18 yo age for kiddushin w/o any basis.”
I mean “made up” based on his own personal observations, opinions, and conclusions, as opposed to a mesorah he received.
“There had to be some rationale for 18yo (versus 17 yo or 19 yo)……it is an age level where he believed that a young man was READY to assume the responsibilities for marriage and presumably, his conclusion was informed by his own experience based on what he knew at the time.”
This is exactly what I mean when I said you hold the tanna (Yehuda ben Teima) made it up based on his own observations of his own time. Which, though he was a wise rabbi, we can disregard to our detriment, CV”S, because “times have changed.” No, in Pirkei Avos and the rest of the Mishna, the tannaim are passing down the mesorah that they received from their teachers. To reduce this to empiricism is devastating, because it closes the door to proper understanding of the Torah and cuts us off from the chain that links us to Har Sinai.
Also, the very next line in the mishna disproves your assertion that the main should already have his parnassa before marriage and children – as it says the pursuit (of parnassa) is at age 20, two years after the age of marriage.