At the end of this morning's service the rabbi did some teaching of his own. (This isn't usual, but through logic that I'll explain if asked and punt otherwise, doing so was useful today specifically.) He brought the mishna about our obligation to remember the exodus from Egypt both during the day and at night. Some of this is in the haggadah; since my family skips that part I was glad to have it here. In short, the torah passage says "all the days", but if it just meant "the days" it could have said so, so "all the days" means day and night. (The torah, like a good technical spec, is not supposed to contain unnecessary words.)
This obligation is fulfilled in the liturgy in the paragraphs after the sh'ma ("I am the lord your god who brought you out of Egypt..."). This passage ends the paragraph about tzitzit (fringes), which (the torah says) we are to wear so that we will see them and remember the mitzvot. We don't wear tzitzit at night (because it says you have to see them; the mishna predates good lighting). So, the rabbi asked, why do we read about tzitzit at night and not just in the morning? He gave Rashi's answer, that we say that paragraph because of the exodus part (and I guess the rest just gets brought along).
I offered a different answer: if we need the fringes to remember the mitzvot, and we need to read about that in the morning even though we're already doing it, then how much the moreso would we need to read that passage at night when we aren't wearing them? To this the rabbi said that I grok talmudic reasoning. :-)
(No, he did not actually say "grok".)