Mission statements, synergies, strategies, visions—they are often ambiguous to the point of being meaningless. Naturally sticky ideas are full of concrete images —ice-filled bathtubs, apples with razors—because our brains are wired to remember concrete data. In proverbs, abstract truths are often encoded in concrete language: “A bird in hand is worth two in the bush.

Even the most abstract business strategy must eventually show up in the tangible actions of human beings. It’s easier to understand those tangible actions than to understand an abstract strategy statement— just as it’s easier to understand a fox dissing some grapes than an abstract commentary about the human psyche.

Abstraction makes it harder to understand an idea and to remember it. It also makes it harder to coordinate our activities with others, who may interpret the abstraction in very different ways. Concreteness helps us avoid these problems. This is perhaps the most important lesson that Aesop can teach us.

For fifty years, The Nature Conservancy (TNC) has helped protect environmentally precious areas in the world using the simplest possible method: It buys them. It buys land at market prices, making it off-limits to environmentally damaging uses, such as development or logging. This strategy has come to be known within TNC as “bucks and acres.” It had appeal to donors and benefactors, because the results of their gifts were so clear. A big gift bought a big piece of land. A small gift bought a small piece of land. As one donor commented, TNC produced “results you could walk around on.”

In 2002, Mike Sweeney, the COO of TNC California, was facing a big challenge. California is particularly important to TNC, because it contains so many environmentally critical areas. California is one of only five Mediterranean climate regions in the world. (The others are the fynbos of South Africa, the matorral of Chile, the kwongan of Australia, and, of course, the Mediterranean.) These Mediterranean climate zones occupy only 2 percent of the world’s landmass but host more than 20 percent of its plant species. If you want to buy environmentally precious land, Mediterranean climates give you a lot of bang for your buck.

In 2002, Sweeney and his staff had taken a map of California and colored in the most environmentally sensitive areas, the areas worth preserving. Astonishingly, 40 percent of the map was colored. This was a non-starter: There weren’t enough bucks out there to buy that many acres.

The students are wisely trying to find a way to break up a big, abstract goal into smaller, more concrete subgoals. This is the right idea. But in this case the numbers are just too big. And “acreage” is not necessarily the best way to think. There are 1,500-acre plots of land that are more environmentally precious than other 90,000-acre plots. Thinking about “acreage per year” is akin to a museum curator thinking about “canvases per year,” without regard to period, style, or painter.

Using concreteness as a foundation for abstraction is not just good for mathematical instruction; it is a basic principle of understanding. Novices crave concreteness. Have you ever read an academic paper or a technical article or even a memo and found yourself so flummoxed by the fancy abstract language that you were crying out for an example?

Or maybe you’ve experienced the frustration of cooking from a recipe that was too abstract: “Cook until the mixture reaches a hearty consistency.” Huh? Just tell me how many minutes to stir! Show me a picture of what it looks like! After we’ve cooked the dish a few times, then the phrase “hearty consistency” might start to make sense. We build a sensory image of what that phrase represents. But the first time it’s as meaningless as 3 + 2 + 1 would be to a three-year-old.

This is how concreteness helps us understand—it helps us construct higher, more abstract insights on the building blocks of our existing knowledge and perceptions. Abstraction demands some concrete foundation. Trying to teach an abstract principle without concrete foundations is like trying to start a house by building a roof in the air.