The well-known expression professional bias appears to date back to the very first years when professions started to exist:
- "Professional bias" designates a mental conditioning brought about by the particularities of one's job. A contrived example is that of a race-car driver, say, who overtakes dangerously when he's out driving in the family automobile with his wife and kids.
Ngram shows that the expression was first used towards the end of the 18th century, roughly during the same years when the first professions were born.
Professional (adj.):
early 15c., of religious orders; 1747 of careers (especially of the skilled or learned trades from c.1793); see profession. In sports, opposed to amateur, from 1846.
professional (n): "one who does it for a living," 1798, from professional (adj.). (Etymonline)
Was the expression coined with the birth of the first professional activities in England or did it already exist in religious contexts where the term profession seems to come from.
Best Answer
A Google Books search for "professional bias" for the period 1700–1800 yields four legitimate matches—all of them connected to religion. From Richard Watson, An Apology for Christianity in a series of Letters, Addressed to Edward Gibbon, Esq (1777):
Bishop Watson's response to Gibbon is cited in Letter 44 of Richard Sullivan, A View of Nature, in Letters to a Traveller Among the Alps (1794):
As Hot Licks notes in a comment below, this is by no means an independent occurrence of "professional bias," but rather a restatement of the previous instance, with Christian substituted for Divine.
From a letter to the Philological Society of London by N. N. on March 7, 1787, in The European Magazine (March 1787):
And from The Parliamentary Register (April 28, 1795):
As two of the four eighteenth-century instances of "professional bias" in the Google Books search results are from bishops, a third quotes one of the first two, and the fourth distinguishes between "men who spent whole lives in the study of Christianity" and men who merely "spent many years in inquiries into it" (arguing that the latter did not have a professional bias), it seems clear that prior to the 1800s the term was understood to refer to religious profession.
The earliest nonreligious (or religion-neutral) instance of "professional bias" in a Google Books search appears in a review of John Fuller, M.D., The History of Berwick upon Tweed, in The Monthly Review (October 1800):
Since the author is a medical doctor and not a divine, I assume that his professional bias is in the direction of modern medicine. The review doesn't mention religion at all.
This rather limited record supports the idea that "professional bias" began as a term connected to the profession (that is to say, the professing) of Christianity and used by various religious and nonreligious writers, and that from there it expanded to include professional occupations or livelihoods within which a particular viewpoint or presumption or interpretive inclination predominates.