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the sea, and, like a new star placed in the sky, keeps the mariner 

 safe upon the great waters. 



On the other hand, when knowledge has been successfully 

 applied to practical purposes, the advance in every direction is so 

 rapid — such gigantic strides are made that we ascribe everything 

 to practice. In contemplating the majestic oak, the little acorn 

 that was buried in the ground centuries before is forgotten. Know- 

 ledge is the seed ; theory is the seed cast into the ground ; practice 

 is the growing plant, and the end is the ripened fruit. Some 

 seeds never germinate ; some theories only require trial to show 

 that they are utterly incapable of producing the end aimed at. 

 Some seeds spring up, but the young plant withers away ; some 

 theories assume a practical shape, but the counteracting causes 

 cannot be eliminated, and the scheme is abandoned. Most seeds 

 spring up and attain perfection ; most knowledge, when applied to 

 useful purposes, produces a rich crop of practical results. Theory 

 without practice is nothing ; and what is practice without theory ? 

 Perhaps a navigator sailing over the seas without sails or steam, 

 without compass or chart — nay, without a ship ; or else a husband- 

 man living on the acorns and arbutes of the holy wood. To 

 recapitulate, practice is the application of knowledge to the 

 requirements of life ; and, according to the general usage, theory 

 is this knowledge at the stage where it has been proposed to apply 

 it to some useful purpose, and before it has been proved to be 

 sufficient as a means to an end. If a formal definition be required, 

 it would be something like this : — -In the business of everyday life, 

 theory is an explanation of the way in which an end may be 

 attained, the explanation being founded on knowledge acquired 

 by scientific investigation, or by deduction from abstract laws, and 

 not in the exercise of the art to which it is proposed to apply the 

 knowledge. Upon comparison it will be seen that the difference 

 between this definition and those given in the preceding papers is 

 more apparent than real. Further, the end of knowledge, or 

 theory — for theory is only a particular phase of knowledge — is 

 practice, and practice is entirely dependent on knowledge or 

 theory. 



