(WineSpectator) - Recently I was doing a signing for my latest book. While scrawling an inscription inside, I was chatting with the person, who waited patiently for me to finish. He flatteringly commented that he had read my columns over the years with enjoyment and then said, “You know, I’ve always wondered what, exactly, makes a wine fine?”

I started to reply by citing features such as finesse and nuance and harmony. But then I stopped. These values, among others such as layers and even a sense of surprise (never mind somewhereness), are all certainly elements that collectively make a wine “fine.” But I stopped because, suddenly, I felt that I was missing the point.

I said, “You know what really makes a wine fine? The root is: It’s not a sure thing.” He looked a bit puzzled, which was understandable. I didn’t have the time to explain it more fully, but I thought it worth mentioning here.

For decades I believed that what separated fine wine from ordinary are features such as complexity and originality. And of course they do. Without them, as well as the elements previously cited, there’s no chance for a wine to rise above the ordinary. But those are really the results, rather than the source.

The source is this business of not being a sure thing. Everywhere in the world, regardless of grape variety or region, fine wine comes from a defiance of guaranteed success.

All of us have been instructed about how great wines come from marginal (for the grape variety) climates where the grape’s reach just barely—but successfully—achieves a full-gripped grasp. This is why, we’re told, Burgundy’s Côte d’Or is so profound for Pinot Noir, why the Médoc is so choice for Cabernet Sauvignon and why Piedmont’s Langhe zone is so singularly triumphant for the Nebbiolo grape. And it’s true.

That the grape has to struggle for ripeness is the traditional axiom for wine greatness. Again, there’s some truth to this, although a more modernist expression might instead talk about the flavor benefit of a long hang time. Whatever.

It all comes down to the same goal of slowly teased-out flavor ripeness without a corresponding loss of refreshing natural acidity. This is not, of course, as easily achieved as it sounds.

All that acknowledged, it still doesn’t capture the idea of “not a sure thing.” Allow me to explain.

One of the recurring features of fine wine in the modern era is, surprisingly, a rejection of scientific assurance. This is surprising if only because so many winemakers and winegrowers are themselves scientifically trained and have no quarrel with the foundational virtues of their training.

Yet many producers have rejected the conventions of science in their planting decisions and winemaking techniques. This has happened almost everywhere fine wine is pursued. The reason is that the pursuit of fine wine leaves them almost no choice.

Science seeks certitude. Scientifically based advice is rooted in a guarantee: You do this and we can assure you that you’ll get this result. We know it for a fact. That’s why it’s science.

For example, when California had to reconstitute its devastated wine industry after the 13 years of Prohibition, which ended in 1933, it turned to a scientific methodology of determining the best place to grow various grapes; based on climate, it was expressed in the concept of degree-days.

With grapevines, growth proceeds only when the temperature achieves 50° F. Every degree above that is counted as one degree-day. When these degree-days are totaled over the several-month span between the beginning of vine growth and the harvest of ripe grapes, the total is called temperature summation. At a glance, one can establish the coolness or warmth of a site or district.