In the branch "_De Partitione Scientiarum_," he divides all human learning into _History_, which uses the memory; _Poetry_, which employs the imagination; and _Philosophy_, which requires the reason: divisions too vague and too few, and so overlapping each other as to be of little present use. Later classifications into numerous divisions have been necessary to the progress of scientific research.
II. Precepts for the interpretation of nature, (_Novum Organum_.) This sets forth "the doctrine of a more perfect use of the reason, and the true helps of the intellectual faculties, so as to raise and enlarge the powers of the mind." "A kind of logic, by us called," he says, "the art of interpreting nature: differing from the common logic ... in three things, the end, the order of demonstrating, and the grounds of inquiry."
Here he discusses induction; opposes the syllogism; shows the value and the faults of the senses--as they fail us, or deceive us--and presents in his _idola_ the various modes and forms of deception. These _idola_, which he calls the deepest fallacies of the human mind, are divided into four classes: Idola Tribus, Idola Specus, Idola Fori, Idola Theatri. The first are the errors belonging to the whole human race, or _tribe_; the second--_of the den_--are the peculiarities of individuals; the third--_of the market-place_--are social and conventional errors; and the fourth--_those of the theatre_--include Partisanship, Fashion, and Authority.
III. Phenomena of the Universe, or Natural and Experimental History, on which to found Philosophy, (_Sylva Sylvarum_.) "Our natural history is not designed," he says, "so much to please by vanity, or benefit by gainful experiments, as to afford light to the discovery of causes, and hold out the breasts of philosophy." This includes his patient search for facts--nature _free_, as in the history of plants, minerals, animals, etc.--nature _put to the torture_, as in the productions of art and human industry.
IV. Ladder of the Understanding, (_Scala Intellectûs_.) "Not illustrations of rules and precepts, but perfect models, which will exemplify the second part of this work, and represent to the eye the whole progress of the mind, and the continued structure and order of invention, in the most chosen subjects, after the same manner as globes and machines facilitate the more abstruse and subtle demonstrations in mathematics."