The New Organon forms part of the great renewal, or Instauratio magna, an ambitious practical and theoretical project to overhaul and reform the way in which man investigates nature. Bacon divides his project into six parts: one) a summary of current knowledge, two) the New Organon itself, which sets out the method to be followed and seeks to prepare the mind for investigation, three) a complete natural history, that will provide the foundations for this investigation, four) examples of the kind of investigation Bacon's method would produce, five) specific practical discoveries that he has made, which serve as a kind of interest payment before the "capital" sum of the complete theory is known, six) the real philosophy, completely explained. Bacon doubts his own ability to complete the project, particularly the last section; he calls for royal patronage to help realize the project. As he imagines it, however, the Great Renewal will reform both epistemology (the philosophy of knowledge) and practice. It will alter the way we think about truth in nature, and how we try to uncover that truth.
Induction is a different method of logic, and a new way of investigating truth. Bacon does not exactly claim to have invented it himself, but does stress its neglect in previous centuries. Unlike the syllogism, which was the dominant logical form after Aristotle, induction begins with natural phenomena and works through a series of intermediate steps to arrive at general axioms or statements about nature. Bacon argues that his method improves upon the syllogism because it begins with concrete things and natures, rather than with words, which can be ambiguous. Also, induction refrains from producing general statements immediately, which serve to confirm impressions already held.
Induction is very different from the modern "scientific" method of testing hypotheses (or guesses) through experiments, but it represents an important development in scientific method. It is important to remember that Bacon himself did not necessarily consider his work to be "science," but rather natural philosophy. Seeing induction only as an inferior version of modern methods is a mistake. Nevertheless, scholars have criticized Bacon's method on several grounds. Mary Hesse argues that Bacon underestimates the importance of hypotheses, and that his method depends on there being a finite number of things with finite natures to be investigated. One could also argue against his assumption that a complete knowledge of nature is necessary for induction to take place; modern scientists and philosophers are far less confident about the possibility for total knowledge.
Experiments form a key part of the New Organon. They are used to investigate nature, and to show how things perform in an unknown situation. This represents a major difference between Bacon and earlier scientific thinkers, who generally used experiments (or thought-experiments) to confirm a previously-held theory. For Bacon, this is a ridiculous notion. Theories can only come from practical experiments and experience of nature. The second book of the New Organon details many experiments performed by Bacon and his assistants, and describes the use of scientific instruments such as the microscope. Lisa Jardine links Bacon to contemporary experimenters such as Gilbert and William Harvey, who discovered the circulation of the blood, and sees him as a predecessor of scientists like Boyle and Hooke. Bacon's emphasis on experiments was perhaps fatal; one account of his death claims that it resulted from catching cold after stuffing a chicken with snow to investigate freezing.
The importance of Aristotle in medieval and early modern intellectual life cannot be underestimated. His works on a wide range of subjects formed the staple of university curricula, and numerous authors approached natural philosophy through his theories. Bacon attempted to end this dominance; he viewed Aristotle as fundamentally wrong-headed, and criticized Aristotle's theories from their logical foundations upwards. He argued that Aristotle needlessly complicated nature by his "dialectics" and distinctions; Aristotelian terminology was more concerned with defending a position in a subtle way than with discovering the truth. Bacon replaced Aristotle's syllogism with induction in his epistemology, and cited Aristotle's work as an example of the Idols of the theater that obstruct rational inquiry. Bacon was by no means the first anti-Aristotelian author—Paracelsus, Ramus, Telesio and Galileo opposed him on various grounds—but he is among the most strident anti-Aristotelians.