v.] IN THE THEORY OF NATURAL SELECTION. 305 



some knowledge of the complex tout ensemble of the lode would 

 be gained. And the more numerous the points of attack, the 

 more complete would be the knowledge acquired, for valuable 

 insight will be obtained in every place where the work is carried 

 on with discretion and perseverance. 



But discretion is indispensable for a fruitful result ; or, leaving 

 our metaphor, facts must be connected together by theories, if 

 science is to advance. Just as theories are valueless without 

 a firm basis of facts, so the mere collection of facts, without 

 relation and without coherence, is utterly valueless. Science 

 is impossible without hypotheses and theories : they are the 

 plummets with which we test the depth of the ocean of un- 

 known phenomena, and thus determine the future course to be 

 pursued on our voyage of discovery. They do not give us 

 absolute knowledge, but they afford us as much insight as it is 

 possible for us to gain at the present time. To go on investi- 

 gating without the guidance of theories, is like attempting to 

 walk in a thick mist without a track and without a compass. 

 We should get somewhere under these circumstances, but 

 chance alone would determine whether we should reach a 

 stony desert of unintelligible facts or a system of roads leading 

 in some useful direction ; and in most cases chance would 

 decide against us. 



In this sense I trust that the sign-post or compass which I 

 offer may be accepted. Even though it should be its fate to be 

 replaced by a better one at a later period, it will have fulfilled 

 its object if it enables science to advance for even a short 

 distance. 



X 



