Bacon (1620/1994) summarized four sources of error that he believed could creep into scientific investigation in his famous “idols”:
■ The idols of the cave are personal biases that arise from a person’s intellectual endowment, experiences, education, and feelings. Any of these things can influence how an individual perceives and interprets the world. Imagine how the stereotypical hungry cowboy and a vegetar- ian might each react to the prospect of seeing beef ribs served at a luncheon.
■ The idols of the tribe are biases due to human nature. All humans have in common the abili- ties to imagine, to will, and to hope, and these human attributes can and usually do distort perceptions. For example, it is common for people to see events as they would like them to be rather than how they really are. The modern philosopher Ludwig Wittgenstein called these innate filters upon our judg- ments our “form of life,” and famously quipped that “If a lion could speak, we could not under- stand him” because the experiences of the lion would be filtered by a nonhuman form of life.
■ The idols of the marketplace are biases that result from being overly influenced by the meaning assigned to words. Verbal labels and descriptions can influence one’s understanding of the world and distort one’s observations of it. Bacon believed that many philosophical dis- putes were over the definitions of words rather than over the nature of reality. Might you feel differently about some position if you learn it is backed by either the Democrats or the Repub- licans? Or, as Shakespeare’s Juliet says of her Romeo—who she should not love just because he is a Montague—“What’s in a name? That which we call a rose by any other name would smell as sweet.”
■ The idols of the theater are biases that result from blind allegiance to any viewpoint, whether it be philosophical or theological. An excellent demonstration of this was conducted by two American psychologists, Albert Hastorf and intermediate between traditional empiricism (sim- ply fact gathering) and rationalism (the creation of abstract principles):