|This article relies on references to primary sources. (January 2011)|
Idola fori is a Latin term, normally translated as "Idols of the Market Place", coined by Sir Francis Bacon and used in his Novum Organum, one of the earliest treatises arguing the case for the logic and method of modern science.
The term is one of four such "idols" which represent "idols and false notions which are now in possession of the human understanding, and have taken deep root therein, not only so beset men's minds that truth can hardly find entrance, but even after entrance is obtained, they will again in the very instauration of the sciences meet and trouble us, unless men being forewarned of the danger fortify themselves as far as may be against their assaults".
Besides idola fori, there are also idola tribus (Idols of the Tribe, coming from human nature itself), idola specus, (Idols of the cave, coming from the tendencies of particular individuals or groups of people) and idola theatri (Idols of the theatre, caused by the influence of philosophers and systems of thought).
But the Idols of the Market Place are the most troublesome of all — idols which have crept into the understanding through the alliances of words and names. For men believe that their reason governs words; but it is also true that words react on the understanding; and this it is that has rendered philosophy and the sciences sophistical and inactive. Now words, being commonly framed and applied according to the capacity of the vulgar, follow those lines of division which are most obvious to the vulgar understanding. And whenever an understanding of greater acuteness or a more diligent observation would alter those lines to suit the true divisions of nature, words stand in the way and resist the change. Whence it comes to pass that the high and formal discussions of learned men end oftentimes in disputes about words and names; with which (according to the use and wisdom of the mathematicians) it would be more prudent to begin, and so by means of definitions reduce them to order. Yet even definitions cannot cure this evil in dealing with natural and material things, since the definitions themselves consist of words, and those words beget others. So that it is necessary to recur to individual instances, and those in due series and order, as I shall say presently when I come to the method and scheme for the formation of notions and axioms.
— Novum Organum, Aphorism LIX
Bacon said that there were two basic kinds of Idol of the Market Place:
They are either names of things which do not exist (for as there are things left unnamed through lack of observation, so likewise are their names which result from fantastic suppositions and to which nothing in reality corresponds), or they are names of things which exist, but yet confused and ill-defined, and hastily and irregularly derived from realities.
— Novum Organum, Aphorism LX
The first kind "is more easily expelled, because to get rid of them it is only necessary that all theories should be steadily rejected and dismissed as obsolete."
But according to Bacon, "the other class, which springs out of a faulty and unskillful abstraction, is intricate and deeply rooted." This is because it has to do with the way words themselves can guide thinking. Nevertheless, there are "certain degrees of distortion and error. [...] some notions are of necessity a little better than others, in proportion to the greater variety of subjects that fall within the range of the human sense."
Bacon said that the Idols of the Market Place were given this name by him because "on account of the commerce and consort of men there. For it is by discourse that men associate, and words are imposed according to the apprehension of the vulgar. And therefore the ill and unfit choice of words wonderfully obstructs the understanding. Nor do the definitions or explanations wherewith in some things learned men are wont to guard and defend themselves, by any means set the matter right. But words plainly force and overrule the understanding, and throw all into confusion, and lead men away into numberless empty controversies and idle fancies."
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