8 ZOOLOGICAL PHILOSOPHY 



only. There is nothing that we can be positive about, except the 

 existence of bodies which affect our senses, and of the real qualities 

 which belong to them, and finally the physical and moral facts of 

 which we are able to acquire a knowledge. The thoughts, argu- 

 ments and explanations set forth in the present work should therefore 

 be looked upon merely as opinions which I propose, with the intention 

 of setting forth what appears to me to be true, and what may indeed 

 actually be true. 



However this may be, in giving myself up to the observations 

 from which my theories have arisen, I have obtained the pleasure 

 which their resemblance to truth has brought me, and I have obtained 

 also the recompense for the fatigues entailed upon me by my studies 

 and meditations. In publishing these observations, together with 

 the conclusions that I have drawn from them, my purpose is to invite 

 enlightened men who love the study of nature to follow them out, 

 verify them, and draw from them on their side whatever conclusions 

 they think justified. 



This path appears to me the only one that can lead to a knowledge 

 of truth or of what comes nearest it, and it is clear that such know- 

 ledge is more profitable to us than the error which might fill its place. 

 I cannot doubt therefore that it is this path which we must follow. 



It may be noticed that I have dwelt with special pleasure on the 

 exposition of the second and especially of the third part of this work, 

 and that I have been greatly interested in them. None the less, 

 the principles bearing on natural history which I have studied in 

 the first part should be looked upon as possibly the most useful to 

 science, since they are in general most in harmony with the opinions 

 hitherto received. 



I might have considerably extended this work by developing under 

 each heading all the interesting matter that it permits of ; but I 

 have preferred to confine myself to such exposition as is strictly 

 necessary for the adequate comprehension of my observations. I 

 have thus spared my readers' time without exposing them to the 

 risk of failing to understand me. 



I shall have attained my end if those who love natural science 

 find in this work any views and" principles that are useful to them ; 

 if the observations which I have set forth, and which are my own, 

 are confirmed or approved by those who have had occasion to study 

 the same objects ; and if the ideas which they succeed in giving 

 rise to, whatever they may be, advance our knowledge or set us on 

 the way to reach unknown truths. 



