SIGNIFICANCE OF THE UNIVERSAL UT NUNC 29 



for these differences. But' what is this exactly? As St. Thomas 

 says: " That nature is, is fer se known, insofar as natural 

 things are manifest to sense. But what the nature of any thing 

 is, or what its principle of motion, is not manifest." ^ 



Meanwhile, we have the name " swan " and whoever knows 

 this name, using it with the meaning agreed upon, does not 

 confuse swans with chickens or geese. Still, there may exist 

 somewhere, or there may have existed, some types of fowl 

 between swans and geese which could make us hesitate about 

 using the name to stand for what is assumed to be a definable 

 nature. The opposition of contradiction between " swan " and 

 " non-swan " is plain enough, but where and how it actually 

 applies may be uncertain. Such is the case whenever the 

 positive term referred to is imperfectly known. Lacking defini- 

 tive knowledge, we have agreed to use the word in a way that 

 is at least in practice meaningful. In the measure that certain 

 sensible signs set swans apart from other feathered creatures, 

 we are confident that our naming has some determinate basis 

 in nature, that swans do in fact have a nature. Just what this 

 is, however, we have to acknowledge that we do not know. 



Let us recognize, however, that even if we knew exactly 

 what a swan is as we know what a plane triangle is, the term 

 " swan " by itself, apart from an enunciation, would be neither 

 true nor false. The same applies to the nominal definition of 

 the name, whether obtained by designation or by description 

 of what it stands for: " a large-bodied, web-footed water bird 

 of the genus Cygnus, having a long neck and sort legs placed 

 far back," etc. We can, of course, go further and state that 

 there are such animals. However, the truth of this statement 

 does not imply that we know exactly what a swan is. Accord- 

 ingly, we are forced to acknowledge a hiatus (a) between the 

 truth of the statement and the relative indetermination as to 

 what a swan is; (b) between the name itself, used to stand for 



" Naturam autem esse, est per se notum, inquantum naturalia sunt manifesta 

 sensui. Sed quid sit uniuscujusque rei natura, vel quod principium motus, hoc non 

 est manifestum." In II Phys., lect. 1, n. 8. 



