All science hitherto, Bacon declares, has been uncertain and unfruitful, and does not advance a step, while the mechanic arts grow daily more perfect; without a firm basis, garrulous, contentious, and lacking in content, it is of no practical value.  The seeker after certain knowledge must abandon words for things, and learn the art of forcing nature to answer his questions.  The seeker after fruitful knowledge must increase the number of discoveries, and transform them from matters of chance into matters of design.  For discovery conditions the power, greatness, and progress of mankind.  Man’s power is measured by his knowledge, knowledge is power, and nature is conquered by obedience—­scientia est potentia; natura parendo vincitur.

Bacon declares three things indispensable for the attainment of this power-giving knowledge:  the mind must understand the instruments of knowledge; it must turn to experience, deriving the materials of knowledge from perception; and it must not rise from particular principles to the higher axioms too rapidly, but steadily and gradually through middle axioms.  The mind can accomplish nothing when left to itself; but undirected experience alone is also insufficient (experimentation without a plan is groping in the dark), and the senses, moreover, are deceptive and not acute enough for the subtlety of nature—­therefore, methodical experimentation alone, not chance observation, is worthy of confidence.  Instead of the customary divorce of experience and understanding, a firm alliance, a “lawful marriage,” must be effected between them.  The empiricists merely collect, like the ants; the dogmatic metaphysicians spin the web of their ideas out of themselves, like the spiders; but the true philosopher must be like the bee, which by its own power transforms and digests the gathered material.

As the mind, like a dull and uneven mirror, by its own nature distorts the rays of objects, it must first of all be cleaned and polished, that is, it must be freed from all prejudices and false notions, which, deep-rooted by habit, prevent the formation of a true picture of the world.  It must root out its prejudices, or, where this is impossible, at least understand them.  Doubt is the first step on the way to truth.  Of these Phantoms or Idols to be discarded, Bacon distinguishes four classes:  Idols of the Theater, of the Market Place, of the Den, and of the Tribe.  The most dangerous are the idola theatri, which consist in the tendency to put more trust in authority and tradition than in independent reflection, to adopt current ideas simply because they find general acceptance.  Bacon’s injunction concerning these is not to be deceived by stage-plays (i.e., by the teachings of earlier thinkers which represent things other than they are); instead of believing others, observe for thyself!  The idola fori, which arise from the use of language in public intercourse, depend upon the confusion of words, which are mere symbols with