Bacon opens by critiquing past approaches to the pursuit of knowledge. Dogmatic scholars shut down further inquiry with their absolute certainty. At the other end of the scale, skeptics assert that nothing can truly be known. Although they used some sound reasoning, their foundations were flawed. The more ancient of the Greeks, whose work is lost, had a moderate approach in between dogmatism and skepticism. Their work was often hindered by expressions of frustration, but they persisted in pursuing the study of nature, optimistic that they could ascertain the truth through practical testing. However, they too lacked a concrete framework for their study, placing too much emphasis on abstract thought.

Bacon then introduces his approach, in which mental reasoning takes the evidence of the senses as its starting point. He asserts that logicians recognize the need for external evidence to support internal reasoning but traditionally apply the senses too late, once the mind has already been shaped. Logic based on flawed premises cannot expose those flaws or establish truth, instead seeming to confirm its own errors. Bacon therefore advocates for an epistemological overhaul, using a set of instructions to direct the mind in its investigations—a “mechanical aid” for investigation.