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.