A PREFATORY LETTER. vii 



answerable for the origination of the doctrine he criti- 

 cises : and the second, that if we are to employ the 

 terms observation, induction, and experiment, in the 

 sense in which he uses them, logic is as much an 

 observational, inductive, and experimental science as 

 mathematics; and that, I confess, appears to me to be 

 a reductio ad absurditm of his argument. 



Thirdly, the Essay " On the Physical Basis of Life" was 

 intended to contain a plain and unteclmical statement of 

 one of the great tendencies of modern biological thought, 

 accompanied by a protest, from the philosophical side, 

 against what is commonly called Materialism. The 

 result of my well-meant efforts I find to be, that I am 

 generally credited with having invented "protoplasm" 

 in the interests of " materialism. " My unlucky "Lay 

 Sermon' 1 has been attacked by microscopists, ignorant 

 alike of Biology and Philosophy ; by philosophers, not 

 very learned in either Biology or Microscopy ; by clergy- 

 men of several denominations ; and by some few writers 

 who have taken the trouble to understand the subject. 

 I trust that these last will believe that I leave the Essay 

 unaltered from no want of respectful attention to all they 

 have said. 



Fourthly, I wish to refer all who arc interested in 

 the topics discussed in my address on " Geological Ee- 

 form," to the reply with which Sir William Thomson has 

 honoured me. 



And, lastly, let me say that I reprint the review of 

 "The Origin of Species ;: simply because it has been 

 cited as mine by a late President of the Geological Society. 



