It was a pleasant visit, not much different from visits I had made through similar plants in Arizona, California and Texas.

As we were about to part, my host told me that his company was not permitted to make structural changes to the building. It was an historic landmark, the former home of a famous 19th-century author.

With the tone you might use to ask a New Yorker if he knows your old friend Jack Smith, who also lives in New York, my host asked, "Did you ever hear of Guy de Maupassant?"

When I replied that I was quite familiar with this wonderful author's touching, surprise-ending stories, my host was astonished. He stared in disbelief that I, an American and an engineer, should know the works of a French writer. When I started to comment on "The Necklace" and "A Piece of String," I was challenging everything he had always believed. It was well-known that Americans were not only arrogant, they were uncouth; they had no culture; they didn't read great authors; they didn't even speak French. Engineers were worse; they understood nothing beyond formulas and circuits. They were solid but boring. Your daughter might want to marry an engineer, but she'd never want to date one.

I had shattered the bedrock of the man's understanding of reality. I had challenged fundamental assumptions. It was almost as if I had challenged the assumption that the earth is round.

Recently, I organized and conducted a couple of focus groups for a semiconductor company. The marketing chief wanted panelist engineers who used his company's kind of chip, which he described with a term that everybody in his company understood. When I suggested that many customers and prospects might not know the term, he smiled condescendingly, then insisted that everybody did.

Came the time of the focus groups, I asked the panelists what the term meant. Nobody knew, though all understood the product.

The marketing chief was astonished. Everybody he knew was familiar with the term; just ask anybody in his company. I had challenged a fundamental assumption, a foundation for his company's selling efforts.

My host in Paris saw reality based on his assumptions. The marketing chief also saw reality built around his assumptions.

Fortunately, some of us don't make assumptions until we test them against the real world.