Samuel Johnson once said that general principles must come from books，which，however，must be brought to the test of real life．The famous remark makes us understand that knowledge we have learnt from books is of great importance，while what is more important is to put it into practice．
    As we all know，most people would study knowledge about science， society and so on from books．Later they start to know the world in general and can deal with some problems properly and reasonably．However，as all old saying goes，“Practice is the sole criterion for testing truth” No matter how brilliant knowledge is，it must be applied to practice so as to examine whether it will work or not．
    In a word，what we should pay attention to is not only the comprehension of knowledge but also the application of it．Only through application can we know the truth of knowledge．People who can’t put knowledge into practical use can't successfully deal with the problems in daily life．