Reply to David Hershey’s Comment, Douglas Allchin

Douglas Allchin

Minnesota Center for the Philosophy of Science and

Program in History of Science and Technology

University of Minnesota

Minneapolis  MN 55455


David Hershey echoes here complaints in the Journal of College Science Teaching 31(May, 2002): 6-7, a journal of the National Science Teachers Association where one may also find my earlier replies, including my citations to van Helmont’s original work.


Let the reader not miss my central theme:  that historical context is critical to understanding how science happens, including experimental design.  Hershey’s present-oriented approach to history (Butterfield 1931) introduces conundrums.  For example, Hershey selects Boyle’s criticism of van Helmont—notably over two decades later—to represent “contemporary” opinion.  If so, why did many individuals at the time (before and including Boyle) repeat the willow tree experiment and discuss its results and method as significant (Brock 1993, 49-53)?  Today perhaps, van Helmont’s concept of ‘gas’ seems “largely unscientific” and thus irrelevant.  How, then, can one appeal to his coining the term in a scientific context as “founder of pneumatic chemistry”?  Is it meaningful to imagine how van Helmont should have interpreted his results in terms of a modern concept of gases?  Assuming that today’s definitions of “science” or “gas” apply throughout history is problematic.  Educators now widely recognize conceptual change as a feature of science (Kuhn 1962).


Hershey’s purpose was “to use a familiar historical experiment as a basis for a discussion of modern experimental design.”  I consider this anachronism as misleading about science.  Discuss modern experimental design, yes.  The potential sources of error are many indeed and central to scientific practice (Allchin 2001).  But nothing is gained by applying modern standards critically to an earlier case based on different norms.  Trying to “correct” the history obscures how science actually happens(ed).  If one is not willing to engage historical context, then do not use history at all.  Pseudohistory—historical facts used piecemeal to prove a point—only misportrays the nature of science (Allchin 2003a, 2003b).


It would be valuable indeed to understand how van Helmont could have isolated a substance we now call carbon dioxide and yet reasonably failed to recognize its role in the tree growth he also studied.  How could he have been both “right” and “wrong”—by our standards?  Merely profiling van Helmont’s flaws and/or faulting him, however, only leads to paradox.  One must get beyond simplistically labeling right and wrong, hero and fool.  One must understand van Helmont himself.  This is where the approach Hershey defends falls short.  Appreciating the context in which van Helmont reasoned from empirical evidence yet could later be considered mistaken constitutes, in my view, a profound lesson in the foundations and limits of experimental design and scientific reasoning (Brock 1993, xxi-xxii).


Regarding Hershey’s continuing concern about being misquoted, I must beg the reader’s forgiveness.  I used quotes to mark a well-known phrase being adapted ironically.  To those who missed the irony, I must apologize.  I also wish to thank the Pantaneto Forum for considering my article worth republishing.






Allchin, D. 2001. Error types. Perspectives on Science 9:38-59.

Allchin, D. 2003a. Lawson’s shoehorn, or should the philosophy of science be rated ‘X’? Science & Education 12:315-329.

Allchin, D. 2003b. Pseudohistory and pseudoscience. Science & Education 12:341-357.

Brock, W. 1993. The Norton History of Chemistry. New York: W.W. Norton.

Butterfield, H. 1931. The Whig Interpretation of History. London: G. Bell and Sons.

Kuhn, T.S. 1962. The Structure of Scientific Revolutions. Chicago: University of Chicago Press.