A priorism is somewhat of a dirty term these days. It is often equated with dogmatism or with intolerance toward empirical research. This is unfortunate because we are all a priorists. The a priorist nature of any scientific discipline, or for that matter, of any knowledge acquisition technique, is embedded in the nature of human communication of knowledge.
The extent to which one human can explain anything to another human is limited by the number of words in the language that these two individuals understand equally. To define the meaning of a word, one must use other words. Then, one may need to define the meaning of every word in this definition using yet other words. To avoid circular definitions, these words must not include the words that we were trying to define initially. If you continue this process, you must conclude that all definitions must be based on a set of words that are assumed to be equally understood by both individuals. The smaller the number of these words that are equally understood, the less one individual can explain to another.
The implication is that the claim that we understand something is based on the assumption that we understand a given set of words. This means that expanding our understanding of the world will require expanding the number of words we assume a priori to be understood.
To illustrate this, let us start with the word square. If we say that a square is a geometrical shape, we are assuming that the meanings of words is, geometrical, and shape are already understood. If they are not understood, we need to define them in terms of other words that are understood. We may define is as a present tense of be. Here, it is either assumed that the words present, tense, of and be are understood, or we need to define them in terms of other words that are understood. You can see that if we are ever to define or explain anything, there needs to be a point at which we stop explaining the meaning of words in terms of other words. At this point, we reach what we may call the ultimate givens, words whose meaning is assumed to be understood a priori (or prior to any knowledge).
This tells us that we all need the belief that some ideas are understood without any explanation. Their meaning is assumed to be given to us. It is thus inappropriate to claim that, for example, economists who are a priorists are somehow fundamentally different from other economists or from other scientists. It is just that a priorists are more transparent about the methodological nature of their knowledge.