276 TEE PRINCIPLES OF SCIENCE. 



law is verified. Much caution, therefore, is desirable in 

 its application. 



Negative Arguments on the Principle of Continuity. 



Upon the principle of continuity we may often found 

 arguments of great force which prove an hypothesis to be 

 impossible, because it would involve a continual repetition 

 of a process ad infinitum, or else a purely arbitrary breach 

 at some point. Bonnet's famous theory of reproduction 

 represented every living creature as containing germs 

 which were perfect representatives of the next generation, 

 so that on the same principle they necessarily included 

 germs of the next generation, and so on indefinitely. The 

 theory was sufficiently refuted when once clearly stated, 

 as in the following poem called the Universe 6 , by Henry 

 Baker : 



' Each seed includes a plant : that plant, again, 

 Has other seeds, which other plants contain : 

 Those other plants have all their seeds, and those 

 More plants again, successively inclose. 



' Thus, ev'ry single berry that we find, 

 Has, really, in itself whole forests of its kind, 

 Empire and wealth one acorn may dispense, 

 By fleets to sail a thousand ages hence/ 



The general principle of inference, that what we know 

 of one case must be true of similar cases, if they really 

 are identical in the essential conditions, prevents our 

 asserting anything which we cannot apply time after 

 time under the same circumstances. On this principle 

 Stevinus beautifully demonstrated that weights resting 

 on two inclined planes and balancing each other must be 

 proportional to the lengths of the planes between their 

 apex and a horizontal plane. He imagined an uniform 



e 'Philosophical Transactions' (1740), vol. xli. p. 454. 



