In Book 2, Bacon starts a fresh list of aphorisms, beginning again at number one. Bacon asserts that the ability to effect change on something is true power and that the ability to understand what that thing truly is represents true knowledge. He states that these two things are interconnected and that learning the first will reveal the second. He suggests this order—commencing with the practical—to avoid being sucked into unfounded abstractions, and he explains how establishing the suitable confines of an experiment will focus the quest for knowledge.

The main principle underpinning his system is therefore that evidence, or things, must be broken down into the smallest possible components to find the primary axioms—small axioms from which larger ones can be built. He then explains that there are two categories of axiom to seek and therefore two types of investigation.

The first type of axiom considers things as composites of their simple features, which can themselves be investigated. For example, when looking at gold, one would list the component characteristics of gold (such as its color, weight, and softness). To try to produce gold, one would therefore try to reproduce these characteristics.

The second axiom considers things as concrete bodies and studies the processes or causes that create them or act on them—for example, considering how gold forms in the earth or how a seed becomes a tree.