"[Our] understanding of them may develop. Now a change of understanding involves a change in explanatory conception, for the explanatory concept may be defined as an expression of the content of the understanding. Yet there is an important distinction between heuristic and explanatory concepts. Fire was conceived by Aristotle as an element, by Lavoisier’s predecessors as a manifestation of phlogiston, and by later chemists as a type of oxidisation. But though the explanations differed, the object to be explained was conceived uniformly as the ‘nature of’ a familiar phenomenon, and without this uniformity it would be incorrect to say that Aristotle had an incorrect explanation of what he meant and what we mean by fire.” (Bernard Lonergan, Insight: A study in Human Understanding, (Vol.3, Collected Works, University of Toronto Press, 2008) p. 759