SCIENTIFIC KNOWLEDGE IS NQT INFALLIBLE. 147 



pleteness of our experience, the very limited and variable 

 power of our senses, and the imperfect action of all our in- 

 tellectual powers, weaken the entire fabric of our scientific 

 beliefs. 



But although the impressions we receive through our 

 senses are often fallacious, and from this cause and from 

 our defective intellectual powers, the conclusions we draw 

 from them are more or less erroneous, we do still possess in 

 science a means of arriving at the most certain truth. We 

 are able by means of our faculties of comparison and reason, 

 to compare those impressions or inferences with each other, 

 detect contradictions and inconsistencies, eliminate error, 

 and gradually impart an ever-increasing degree of truth- 

 fulness and certainty, even to our most fundamental scien- 

 tific axioms and beliefs. It is by a laborious process of 

 this kind, that much of our scientific knowledge has had 

 imparted to it its present high degree of certainty ; and as 

 the process in itself appears to be a perfect one, we may 

 reasonably hope, by a continuation of it through an im- 

 mensity of time, to arrive at an extreme degree of cer- 

 tainty and completeness in scientific matters. By the 

 same process as we have already arrived at what are termed 

 f axioms ' in science, shall we be able to arrive at an ever- 

 increasing number of truths upon which we may rely 

 reasonably with an equal degree of security. As an immense 

 number of natural truths, probably including some of the 

 greatest, remain still unknown, that which we suppose to 

 be truth requires to be tested afresh by every accession of 

 new knowledge, and in this way our beliefs are continually 

 being purified ; but in questions where no effectual test 

 can be applied, the most certain truth cannot be obtained. 



Notwithstanding, also, all the errors to which our 

 senses and intellectual powers are liable, reason has in this 

 way, during all human existence, proved itself a true rock 



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