Years ago, a professor of philosophy introduced me to a concept that has helped me make business decisions time and again.

We were discussing Nietzsche, the German philosopher and poet. I knew a little bit about Nietzsche. I knew that he was anti-religion (as we say today) and believed that man could perfect himself by self-assertion. But it was what he had said about the decision-making process that intrigued me. Specifically, according to the professor, he predicted that assumptions made from secondary knowledge (what we learn from studies, books, newspaper accounts, etc.) as opposed to primary knowledge (what we learn from experience) would one day replace experience as the basis of judgment.

I had never given much thought to the distinction between primary and secondary knowledge. But after our discussion, I realized that many of the opinions that I held were, indeed, based on information that I had read, not on personal experience. And the more I thought about it, the more I have become convinced that Nietzsche was right.

In fact, I think it’s fair to say that Nietzsche’s prediction has already come true. Because it seems that these days, most people, most of the time, are making important decisions based more on secondary knowledge (Nietzsche called it wissen) than on knowledge from personal experience (erfahrung).

It’s understandable.

There is so just much information out there. Every day, we are bombarded with facts and figures from the media. And it’s incredibly easy to research just about any subject on the internet. Often, what we learn confirms our own experiences. Sometimes, it contradicts them. But here’s the problem. Instead of using our experience to judge the validity of all of that secondary information, we tend to judge the validity of our own experience by what we’re reading and hearing.

 In business, for example, I know from experience that when I invest in something that I know little or nothing about, I lose money. Yet, I can talk myself into making such an investment if I am shown a business plan that is loaded with impressive numbers. (Even though I know, also from experience, that numbers can be rigged to support almost anything.)

In fact, when I think about bad decisions I’ve made in business, it was most often because I allowed myself to favor the wissen (the outside knowledge) over the erfahrung (the knowledge in my bones).

Case in point: A former business partner and I spent a year attempting to succeed with a publication aimed at new mothers. We were convinced – by the numbers we had come up with – that it was going to be a huge winner for us. The fact that neither of us had any experience in that segment of the industry didn’t faze us.

The result: We were a quarter of a million in the red before we gave up.

Another example: I’d always liked the idea of being an art dealer. So when I first retired, I bought a half-interest in a dealership in Boca Raton. I had read everything I could get my hands on about how to make a success out of that business, and I was confident that I could do it. But what I didn’t know – what no amount of research could have prepared me for – was the day-to-day reality of selling art. It took just a few weeks for me to realize that it’s not about sitting in an elegant gallery and answering erudite questions posed by wealthy people stopping by. It’s about high-pressure selling tactics that I just didn’t have the stomach for.

The result: I bailed. (Needless to say, my partner was happy to see me go.)

I’m not saying you should ignore secondary knowledge when making critical decisions. But when it’s wissenvs. erfahrung…  trust your bones.

Will you ever miss out on a great opportunity? Maybe. But my experience tells me that you’ll go broke before you succeed at something you don’t understand on a gut level.