Bacon did not think the human mind was a "tabula rasa" which was able to receive such a correct image of the world.

Instead it was more like a crooked mirror due to inherent distortions.
So before trying to pursue knowledge a person has to improve his mind.

He described the common prejudices that prevent people from having the clarity of mind necessary to discover this knowledge as four "Idols" (idola):

"Idols of the Tribe" (idola tribus), which are common to everyone due to the imperfection of human nature such as our easily deceivable senses, a tendency to wishful thinking and rushing to judgment.

"Idols of the Cave" (idola specus), are the parochial and usually unexamined assumptions a person has acquired from their culture, gender, class, religion, upbringing and education.

"Idols of the Marketplace" (idola fori), coming from the confusions inherent in language such as words for things that do not exist or words that are vague. In this Bacon seems to have anticipated Wittgenstein.

"Idols of the Theater" (idola theatri), which result from the fictional worlds created by dogmatic philosophy that has not been subjected to testing by experimentation.
He describes these as superstitions and offers as an example people who base their natural philosophy on the Book of Genesis, Chapter I.