400 A SHORT HISTORY OF SCIENCE 



Whatever, in connection with my professional practice or not in 

 connection with it, I may see or hear in the lives of men, which ought 

 not to be spoken abroad, I will not divulge, as reckoning that all such 

 should be kept secret. 



While I continue to keep this oath unviolated, may it be granted 

 to me to enjoy life and the practice of the art, respected by all men at 

 all times ; but should I trespass and violate this oath, may the reverse 

 be my lot. 



B. THE OPUS MAJUS OF ROGER BACON (1267 A.D.) 

 [AN ANALYSIS OF THE SIXTH PART. BY J. H. BRIDGES.] 



Of all the parts of the Opus Majus, the sixth is the most important. It treats 

 of experimental science, domina omnium scientiarum et finis totius specula- 

 tionis. Without experience, as Bacon constantly repeats, nothing can be known 

 with certainty. Even the conclusions of mathematical physics, reached by argu- 

 ment from certain principles, must be verified, before the mind can rest satisfied. 

 To this great science all the others are subsidiary; they are to it ancillae or hand- 

 maids, an expression that curiously reminds one of Francis Bacon. The reason- 

 ing in favour of experience is well worth quoting at length : 



" There are two modes in which we acquire knowledge, argument and experi- 

 ment. Argument shuts up the question, and makes us shut it up too; but it gives 

 no proof, nor does it remove doubt and cause the mind to rest in the conscious 

 possession of truth, unless the truth is discovered by way of experience, e.g. if any 

 man who had never seen fire were to prove by satisfactory argument that fire burns 

 and destroys things, the hearer's mind would not rest satisfied, nor would he avoid 

 fire; until by putting his hand or some combustible thing into it, he proved by 

 actual experiment what the argument laid down; but after the experiment had been 

 made, his mind receives certainty and rests in the possession of truth, which could 

 not be given by argument but only by experience. And this is the case even in 

 mathematics, where there is the strongest demonstration. For let any one have the 

 dearest demonstration about an equilateral triangle without experience of it, his 

 mind will never lay hold of the problem until he has actually before him the inter- 

 secting circles and the lines drawn from the point of section to the extremities of a 

 straight line. He will then accept the conclusion with all satisfaction." (Op. 

 Maj., p. 445 [ed. Bridges, ii. 167}.) 



This important passage, it seems to me, marks a distinct advance in the philos- 

 ophy of science. The science of that time proceeded wholly per argumentum; 

 verification was unknown. Not only, however, does Bacon recognize the necessity 

 for experiment, for observation at first-hand, but he has a clear appreciation of the 

 true nature of scientific verification. He has already expounded his ideal of 

 physical science, the application of mathematics to determine the laws of force 

 and to deduce conclusions from these laws; but he is perfectly aware that these 



