I have said that the only difference between experts and non-experts is that experts have some knowledge that non-experts do not have. Not all experts are equal. There is no great gulf between experts and non-experts. Rather, there is a gradual increase in expertise as we move from non-experts to experts. Similarly, experts in one subject may be average people in another. All experts are experts in comparison to someone else who does not know as much about the answer to a particular question as they do.
All experts are experts in comparison to non-experts. Consider a person named Bob who wants to know the answer to a particular question. He does not know the answer. The question is “What kinds of stars are there?”. I know something about what kind of stars there are. So in relation to Bob on that particular question, I am an expert. However, my knowledge is that of an amateur compared to those who have graduate degrees in astronomy. They are experts compared to me. So I am a non-expert when compared with them, and an expert when compared with Bob. What makes the difference is who knows more about the question. The person who knows more is the expert.
All experts are experts in relation to a particular question. Biologists are those experts who know more about the answer to the question “What are living things?” than non-biologists do. Similarly, someone could be an expert on neutron stars in the same way. Anything that someone is an expert on is an answer to some kind of question. If it is a subject, then they know what that subject is. If is it why something happens, then they know why.
All of this is about experts in general. However, we often speak of experts absolutely. For example, we believe that a person is an expert on a particular subject if they have a doctorate in it, have studied it for a long time and have written books and articles showing that they understand it. It is these sort of people that the average person is talking about when they talk about experts. General experts ask a question and may have experts who know more than they do about it in every way. Experts do not. Experts have at least one question that they know the answer to and no one else knows that answer except by means of them. Let’ s refer to the first kind of experts as relative experts, and the second kind of experts as experts.
Both relative experts and experts are experts about the answers to particular questions. They both are experts in comparison to others in relationship to that question. This conclusion has important consequences: experts are only experts about some particular topic and experts are people who know more rather than people who are infallible. We also have to remember that experts are fallible people who sometimes think irrationally about their subject just like anyone else does. But that is another topic.