My daughters are nine and 12 years old, a time of personal omniscience. Children this age bounce facts around like rubber balls. Do I know how old the earth is? Can I explain why Pluto isn't considered a true planet? Because I can't conjure answers to these and other questions, they doubt my legitimacy as an authority figure.

It's easy to feel all-knowing when you can remember everything you've ever been taught. It's only later in life that the mind becomes crowded with facts, so many facts that a person begins to forget. It's knowing you have forgotten something which allows doubt to soften arrogance. Maturity is little more than comprehending the depth and breadth of all you have forgotten.

If you took all the facts I once knew but have since lost, and turned them into grains of sand, they could blanket a small beach. Some I've lost to the erosion of time, others I've actively repressed. Either way, they are gone–and good riddance. Of all the lessons I've learned in life, I've chosen to retain fewer than a dozen. Everything else I can look up in reference books when I need to.

I know how to do arithmetic. For a few years I deliberately forgot how to subtract. In this age of calculators I judged subtraction an unnecessary skill. I was wrong. I had to relearn subtraction when my oldest daughter entered first grade.

I know that nothing beats a good encyclopedia when it comes to finding facts, but whatever you're looking for, it won't be in there. I know that vehicular right-of-way works best when ceded, not claimed, and I know you can exercise every morning and never get thin, but if you snack every night you'll surely grow fat.

I know that food is medicinal. You can treat a mild depression with chocolate, but a case of the blues lasting longer than a week requires something baked, frozen or fried. And everyone knows there are two kinds of food: the kind your mommy made to cheer you up when you were a child, and everything else.

I understand the essential paradox to parenthood: Each second you spend helping your children with homework or listening to quarrels lasts an eternity. But the sum of all those eternities passes in the blink of an eye.

I know that love is a verb, not a noun. You don't own someone's love like you posses a purse or a car. You must love other people actively and deliberately. Unconditional love is rare and wonderful, and is one of the few things in life you can neither earn nor refuse. It is made manifest because someone wills it to be so. It's the closest thing in this world to magic, and like a fairy tale spell, it can be removed only by the one who conjured it.

I know I love my children unconditionally.

I know that friendship is built on trust as much as honesty. When it comes to friends, not every criticism is meant to hurt, and not every compliment is given sincerely. When your friend asks if her $200 dress makes her look fat, she trusts you'll lie if necessary.

I know the world was brought to life as a deliberate act of creation by a force I can neither comprehend nor identify. I don't assert this as a factual event, but I have faith. Faith is a paradox which has value only in the face of ambiguity. When the facts are certain, faith is supplanted.

These are the matters I know with certainty: love, friendship, faith and food. They're not flashy and they don't impress my children, but they're lessons which have sustained me through passing time and changing circumstance. One day even these few kernels of knowledge may slip from my memory. By then, I hope I've passed them to my daughters. That's the best they can hope to get from me; I plan to spend the rest of their inheritance.

And for the record, the Earth is 4.6 billion years old. I would have baked a birthday cake but the candles might have melted Pluto which is--after all--merely a chunk of cosmic ice and not a planet in the true sense of the word.

KATHY PURCELL is a professional newspaper columnist and mom who is active in the Internet writing community.