He wants a child’s heart, but a grown-up’s head.

Prudence means practical common sense, taking the trouble to think out what you are doing and what is likely to come of it.  Nowadays most people hardly think of Prudence /as one of the ‘virtues’.  In fact, because Christ said () we could only get into His world by being like children,many Christians have the idea //that, provided () you are ‘good’, it does not matter /being a fool.  But that is a misunderstanding.  In the first place, most children show plenty of ‘prudence’ about doing the things () they are really interested in,and think them out /quite sensibly. * think something out ; to consider or plan something carefully. In the second place, as St Paul points out, Christ never meant that we were to remain children in intelligence: on the contrary.  He told us to be not only ‘as harmless as doves’, but also ‘as wise as serpents’.  He wants a child’s heart, but a grown-up’s head.  He wants us to be simple, single-minded, affectionate, and teachable, as good children are; but He also wants [every bit of intelligence () we have] [to be alert at its job, and in first-class fighting trim].  [The fact //that you are giving money to a charity]does not mean that you need not try [to find out whether that charity is a fraud or not].  { The fact //that [what you are thinking about] is God Himself }(for example, when you are praying)does not mean that you can be content with the same babyish ideas //which you had when you were a five-year-old.  It is, of course, quite true that God will not love you /any the less, or have less use for you, if you happen to have been born with a very second-rate brain.  He has room /for people with very little sense, but He wants every one to use what sense they have. From Mere Christianity Compiled in A Year with C.S. Lewis