Bacon's Essays offer a comprehensive plan to overcome "the deepest fallacies of the human mind.” (Works 4.431). These fallacies he calls the Idols. The doctrine of Idols is most clearly formulated in Bacon's Novum Organum but this is only the final articulation of a conception of human understanding within which he had written for several years. Throughout his work, notably in 1605's Advancement of Learning, he refers to the Idols. There he calls them "false appearances" (4.431).
By the time the doctrine of Idols is fully articulated in the Novum Organum it is divided into four classes: "the first class Idols of the Tribe; the second, Idols of the Cave; the third, Idols of the Market-place; the fourth, Idols of the Theatre" (4.53).
The Idols of the Tribe hinder humankind by perverting our collective perception of reality. Instead of coming to know reality directly, we encounter it through a nature peculiarly human which tends to "distort and discolour the nature of things by mingling its own nature with it" (4.54). This "own nature" distorts "the nature of things" through its tendency to perceive and accept evidence which supports beliefs over evidence which tends to refute those same beliefs.
The Idols of the Cave are peculiar to each individual. They manifest themselves, for example, as the tendency to remark similarities between things even when disparities are the more essential characteristics, or contrarily, the tendency to note the differences between two or more things that are essentially the same (4.59). Bacon also uses the Idols of the Cave to account for our tendency to perceive the world according to our own particular interests. As the Idols of the Cave are undoubtedly an allusion to Plato, it is no surprise that as an example Bacon argues that Aristotle's particular interest in logic over-rode and distorted his understanding of natural science (4.59). In modern literary studies, we might see the particular interest in a given critical paradigm, for example the psycho-analytical, as distorting a critic's reading of literature.
Bacon created the term "Idols of the Market-place" to encapsulate his belief that "the ill and unfit choice of words wonderfully obstructs the understanding" (4.55). . . . Bacon chose the name "Idols of the Market-place" because he felt that "words are imposed according to the apprehension of the vulgar" (4.55) and the Market-place epitomizes the realm of contact between the vulgar and the refined. We can certainly see both the apparent "love of the lie itself" and "wonderful obstruct[ion of] the understanding" in the most visible element of the modern market-place: advertising. It often seems that the predominant philosophy of modern advertising is to obstruct the understanding as "wonderfully" as possible.
The Idols of the Theatre are the most obviously adscititious (i.e. not innate, "adopted from without") class of Idols and are "plainly impressed and received into the mind from the play-books of philosophical systems and the perverted rules of demonstration" (4.62). "The Idols of the Theatre" describes our "tendency to assent to forms - logical, rhythmical, syntactical -rather than to empirical evidence" (Fish, 85). In addition to taking these "forms," the Idols of the Theatre are the received notions of various (philosophical and religious) dogmas, and what we have lately called "conventional wisdom."
Bacon, Francis. The Works of Francis Bacon, 7 vols., eds. James Spedding, Robert Leslie Ellis, and Douglas Denon Heath. Stuttgart-Bad Cannstatt: Friedrich Fromann Verlag Gunther Holzboog, 1963.
Fish, Stanley E. Self-Consuming Artifacts, Berkeley: University of California Press, 1972.