118 



of matter, the raw material with which we work, and amid the 

 actions and interactions of what we call the physical forces, can we 

 know what we are to do to arrive at any given result 1 Clearly but 

 by the possession of a knowledge of those varied properties and 

 actions. Now that knowledge, which is clearly so desirable, we 

 call science, or when implying practice, theoretical knowledge — 

 that is, the knowledge necessary to enable us to form theories or 

 explanations of natural phenomena. We therefore arrive at the 

 conclusion that to plan correctly we should be in possession of 

 sound theoretical knowledge, or in other words — of a knowledge 

 of those facts and abstract principles of nature which we call 

 science. But planning is only one part of an operation. Our 

 plans, to be useful, require carrying out, and for that purpose it is 

 clear that we should possess a thorough knowledge of tools, of 

 their use and application. Now that knowledge we call practice 

 when we use the word in connection with theory, although it is 

 sometimes used in that connection in the sense of experience, 

 which is clearly wrong, because experience includes both thinking 

 and doing, while practice has only reference to the latter. The 

 relation in which theory and practice stand to each other — that is 

 what we set out to find — is therefore that of planning and executing 

 or thinking and doing, both of which operations are included in 

 everyone of our works and actions that are not purely automatic. 



Theory and practice are therefore, what I said before, 

 reciprocal parts of a unity — expressions of operations whose con- 

 junction is essentially necessary for the useful and efficient effect 

 of either of them. For as thinking is useless unless it be carried 

 out in action, so is theory useless without practice. And as doing 

 without thinking may result in a great waste of time, material, and 

 energy, so may practice without theory. Moreover, as doing 

 without thinking resembles the action of a machine, so practice 

 without theory could not possibly be progressive, but would repeat 

 itself again and again. The arts would at once come to a stand- 

 still, and with them the whole moral and intellectual progress of 

 man. Again, as we know of no doing that is not accompanied by 

 some thinking, so there is no practice but is preceded by more or 



