36 THE SCIENCE OF LOGIC 



strides which physical science has made since the Renaissance ? Many good 

 reasons may be assigned. 



One is that in those ages philosophers were more preoccupied with the 

 philosophy of mind than with that of external nature, with the application of 

 reason to principles accepted on authority, with the explanation of revealed 

 religion and the unfolding of the contents of the Divine deposit of Revelation 

 by means of philosophical principles and methods (203). And, as the full mean 

 ing and proper understanding of those great truths and principles are arrived 

 at by the application of the deductive or synthetic method, the attention of 

 those philosophers was not arrested ^y the possibilities of knowledge that 

 might have been opened up through a more careful analysis of the complex 

 phenomena of external nature. 1 



But another, and more important, consideration is that they had not the 

 means of prosecuting such an analysis. They knew the method theoretically, 

 but this knowledge in itself was of little use. When there is question of estab 

 lishing a law of Physical Nature such as the laws of the planetary motions, 

 or of the refraction of light it is not enough to know that &quot; a non-free cause 

 cannot regularly produce an effect that is opposed to its natural tendency, an 

 effect it is not determined by its nature to produce,&quot; &quot; causa non libera non 

 potest producere ut in pluribus effectum, ad cujus oppositum ordinatur, vel 

 ad quern ex forma sua non ordinatur &quot;. This abstract, hypothetical principle 

 merely asserts that if &quot; necessary &quot; or &quot; non-free &quot; causes exist, causes predis 

 posed by an internal tendency (&quot;forma &quot;) to produce definite effects, the latter 

 will occur with the regularity of a &quot; law &quot; ; but it does not of itself authorize us 

 to assert categorically that there are such internal tendencies or principles of 

 finality in nature, that there are causes predisposed to manifest such fixed, 

 unchanging activities (cf. 223) ; and still less to affirm with certainty that this 

 or that oft-observed combination of particular phenomena is the expression 

 of some one of those causal tendencies existing in nature. 



Such a categorical conclusion as the latter can be justified only by a dili 

 gent observation of the natural phenomena to which it refers. And nature is 

 infinitely complex : so that the establishment of a certain conclusion that this 

 series of phenomena reveals this universal physical law, necessarily presup 

 poses a detailed and accurate weighing, reasoning, analysing, and comparing 

 of all the elements that enter into the phenomena in question. The phe 

 nomena of physical nature exist in space and time : accurate quantitative 

 measurement is, therefore, at the basis of all experimental research : and hence, 

 the discovery of instruments for delicate measurement was an indispensable 

 condition for the progress of the physical sciences. But Aristotle and the 

 mediaeval Scholastics had neither the clock for the accurate measurement of 

 time, nor the balance for the exact estimation of weight, nor the thermometer 

 for measuring temperature, nor the barometer for measuring atmospheric 

 pressure, nor the telescope to observe the heavens, nor the microscope 

 to reveal the mysteries of the minute structure and composition of organic 

 tissues. It is true, indeed, that the sagacity of great genius, the patience of 

 long reflection, and disinterested zeal in the pursuit of truth, can contribute 

 much, even with the aid of mere ordinary observation, to the development 

 of scientific speculation : witness the wonderful perfection of the Ptolemaic 



1 Cf. CLARKE, Logic, p. 480. 



