Yesterday morning, on the ride in to school, my son asked me why I sometimes send him emails about a certain aspect of machine learning. “All my free time goes to my math homework or soccer,” he said. “Why do you think I have time to work on some random machine learning problem?” He also may have called me weird.

I told him that I had no interest in taking up his free time; instead, I was inviting him to make soup with me.

My daughter, who was tuning the radio at the time, chimed in. “Soup or soup.” (Yes, she has a certain tilt to her voice when she she’s speaking in italics.)

“Soup,” I said.

“What’s with all the metaphors?” she asked.

“All the metaphors? That’s a longer conversation. This metaphor is important,” I said, “because it connects to one of the greatest things in the world: the generation of new ideas.”

They were both glad when the ride was over before I could say more . . . and one of them may have even remarked (politely, of course), “why don’t you just write a blog post about it!” I think I will.

Here’s the soup theory of idea generation for anyone who wants to continue the ride:

I believe, based on long practice, that it is helpful to think about a topic or idea as a big pot of soup. (This is assuming you don’t need to move quickly.)

When you’re just setting out to make soup, there’s likely some intense heat involved. In terms of an idea, the “tenor” of our metaphor, we might think about this as the initial trip down the rabbit hole or the emotional experience that puts an idea onto your radar in the first place. In terms of cooking soup, the “vehicle” of our metaphor, it’s more literal: you bring the initial stock to a boil.

Once the soup / idea reaches a boil / flashpoint, you move it onto the back burner / file.

You turn the heat down. You let it bubble and gurgle ever so slightly. You expose it, in other words, to time and the lowest possible amount of warmth to keep it cooking. The slower and lower the better, in fact, and you can always turn off the stove completely and just put a lid on the pot.

And now I hear my son’s voice, if I had been explaining this concept to him: “Why the heck do you have to keep sending me emails if the soup is already cooking?”

You have to think of the emails as new ingredients — things you stumble upon while looking around in the kitchen, while maybe doing something else, while maybe traveling somewhere, all while the soup cooks. Once you understand the base, and know it’s cooking, you enter the world a bit differently. Ingredients you meet along the way remind you of the soup, and that it’s cooking. You wonder what would happen if you added those ingredients to the soup. You bring them home and approach the pot. You give the soup a stir, taste it to determine how much of the new ingredients are worth adding. Or, if you’re in a rush, you just toss in the whole bundle. You leave the soup again — and again — and go back to your life. The bundle unfurls and spreads, mixing into the soup.

More life equals more ideas, means more time is passing, means the soup is getting deeper and richer, means more ingredients to add to the soup, means, ultimately, more and more layers and flavors, more blending.

At some point, when you have the time and energy, or when the soup smell is filling up your house so much that you need to do something, you’ll finish the soup. You’ll taste it again. You’ll add some salt, some pepper. You’ll pour it into bowls, select the perfect loaf of bread to go with it, and share it with close friends or colleagues or neighbors or the world. It’s then that you’ll know what the soup is worth, what it might be good for. Or it will just be a nice meal, which is fine, too. Not all soup needs to change the world.

And the point is, you couldn’t have rushed any of that. Not the making; not the serving; not the valuing. It wouldn’t be the same kind of soup — that is, precisely your soup, a soup made of your one, true life — unless it bubbled and gurgled through time and temperature shifts and surprise ingredients and more time.

“So,” I’d be saying to my son right about now if he were listening, “don’t think of them as emails. Think of them as things you might put in a soup . . . a soup we don’t have to serve anytime soon. In fact, the longer we wait, the better the soup. Have a great day at school.”