66 THE POPULAR SCIENCE MONTHLY. 



abound in his writings always remind me of certain cloud-forms 

 which may sometimes be seen in the western sky, especially over 

 horizons of the sea. They are often most glorious and imposing. 

 Oreat lines of towers and of far-reaching battlements give the 

 Impression at moments of mountainous solidity and strength. 

 But as we gaze upon them with wonder, and as we fix upon 

 them a closely attentive eye, the edges are seen to be as un- 

 steady as at first they appeared to be enduring. If we attempt 

 to draw them we find that they melt into each other, and that 

 not a single outline is steady for a second. In a few minutes 

 whole masses which had filled the eye with their majesty, and 

 with impressions as of the everlasting hills, dissolve themselves 

 into vapor and melt away. 



Such are the cloud-castles which mount upon the intellectual 

 horizon as we scan it in the representations of the mechanical 

 philosophy. Nothing can be more fallacious than the habit of 

 building up definitions out of words so vague and abstract that 

 they may signify any one of a dozen different things, and the 

 whole plausibility of which consists in the ambiguity of their 

 meanings. It is a habit too which finds exercise in the alternate 

 amusement of wiping out of words which have a definite and 

 familiar sense, everything that constitutes their force and power. 

 Let us take, for example, the word "function." There is no 

 word, perhaps, applicable to our intellectual apprehensions of 

 the organic world, which is more full of meaning, or of meaning 

 which satisfies more thoroughly the many faculties concerned in 

 the vision and description of its facts. The very idea of an or- 

 gan is that of an apparatus for the doing of some definite work, 

 which is its function. For the very reason of this richness and 

 fullness of meaning, in this word conjoined with great precision, 

 it is unfitted for use in the vapory cloud-castles of definition 

 which are the boasted fortresses of ideas purely physical. And 

 yet function is a word which it is most difficult to dispense with. 

 The only alternative is to reduce it to some definition which 

 wipes out all its special signification. Accordingly, Mr. Herbert 

 Spencer has defined function as a word equivalent to the phrase 

 "transformations of motion"* — a phrase perfectly vague, ab- 

 stract, and equally applicable to function or to the destruction 

 of it, to the processes of death or the processes of life, lo Ihe 

 phenomena of heat, of light, or of electricity, and completely de- 

 nuded of all the special meanings which respond to our pticep- 

 tion of a whole class of special facts. 



Of course the attempt breaks down completely to describe 

 the facts of nature in words too vague for the purpose, or in 

 words rendered sterile by artificial eliminations. It is not Dar- 



* " Principles of Biology," toI. i, p. 4. 



