Now if we but change intonation and instead of knowing _all_, say _knowing_ all, we shall get a little step nearer the standpoint from which the question looks more attackable. The question turns first about that much abused word "knowledge." We generally think it to mean the conviction or even certainty, that under given conditions of things some unavoidable result took place, and will take place anew when those conditions will re-occur. A doctor knows that for a certain illness, the name of which implies a certain condition of the human body, a certain remedy will reëstablish other conditions called health. An engineer knows by experiment and calculation, that a certain form of structure under given loads will have to resist such and such forces in its divers parts, and then he lodges his material in such a way, that no part gets too much and no material gets too little anywhere, which he can only do approximately. But all this is not real knowledge and neither the doctor nor the engineer knows what that thing is he is dealing with and how its molecules feel. Real knowledge has nothing to do with apparent knowledge, and it is useless to ask the real man within to write out the development of a mathematical problem for you. But when it comes to the application of such a mathematical solution whereby one tries to get a certain insight into nature, then it may be said that the real man has that insight into nature without passing by the tedious way of a mathematical investigation.