… is from page 70 of Vol. 12 – Economic Inquiry and Its Logic  (2000) – of The Collected Works of James M. Buchanan; specifically, it’s from Jim’s 1981 article, co-authored with Geoff Brennan, “The Normative Purpose of Economic ‘Science’”:
By its very nature, intellectual activity involves coming to terms with a chaos of observations through the imposition of an order which is itself an artifact of the mental process.
Indeed. So anyone who proclaims that he or she is guided without any priors or presumptions only by “the facts” or exclusively by “the data” is someone who is both insufficiently self-aware and inadequately philosophical. Such a person is destined to be a poor thinker and analyst, having adopted his or her theory haphazardly (or even unawares).
In the above quotation, Buchanan and Brennan do not offer a recommendation for how best to do science; instead, they describe an unavoidable reality that must be lived by anyone who does, or who attempts to do, science (or any sort of intellectual activity). Such priors and presumptions are not optional. The “imposition of an order which is itself an artifact of the mental process” – note carefully the word “artifact” – is literally unavoidable. Therefore, the chief issue is not whether a scholar or thinker or analyst or scientist will or will not have theoretical priors and presumptions that affect both the questions that he or she asks and the manner in which he or she interprets empirical reality; the chief issue is just what those theoretical priors and presumptions will be.