2/o OF THE ADVANCEMENT OF LEARNING 



potentials man's inquiry may be the more awake in deduc- 

 ing direction of works from the speculation of causes. 

 And secondly, that those experiments be not only esteemed 

 which have an immediate and present use, but those 

 principally which are of most universal consequence for 

 invention of other experiments, and those which give most 

 light to the invention of causes ; for the invention of the 

 mariner's needle, which giveth the direction, is of no less 

 benefit for navigation than the invention of the sails, which 

 give the motion. 



Thus have I passed through Natural Philosophy, and 

 the deficiences thereof; wherein if I have differed from the 

 ancient and received doctrines, and thereby shall move 

 contradiction ; for my part, as I affect not to dissent, so I 

 purpose not to contend. If it be truth, 



Non canimus surdis^ respondent omnia syhae: 



the voice of nature will consent, whether the voice of man 

 do or no. And as Alexander Borgia was wont to say of 

 the expedition of the French for Naples, that they came 

 with chalk in their hands to mark up their lodgings, and 

 not with weapons to fight ; so I like better that entry of 

 truth which cometh peaceably with chalk to mark up those 

 minds which are capable to lodge and harbour it, than that 

 which cometh with pugnacity and contention. 



But there remaineth a division of Natural Philosophy 

 according to the report of the inquiry, and nothing con- 

 cerning the matter or subject ; and that is Positive and 

 Considerative ; when the inquiry reporteth either an 

 Assertion or a Doubt. These doubts or non liquets are of 

 two sorts, Particular and Total. For the first, we see a 

 good example thereof in Aristotle's Problems, which 

 deserved to have had a better continuance, but so never- 

 theless as there is one point whereof warning is to be given 

 and taken. The registering of doubts hath two excellent 

 uses : the one, that it saveth philosophy from errors and 

 falsehoods ; when that which is not fully appearing is not 

 collected into assertion, whereby error might draw error, 

 but reserved in doubt : the other, that the entry of doubts 



