It is that he cannot have too little to do with people who are too deep for him and cannot be too careful of interference with matters he does not understand--that the plain rule is to do nothing in the dark, to be a party to nothing underhanded or mysterious, and never to put his foot where he cannot see the ground. 
It is that he should have nothing to do with people who are too deep for him, and cannot be too careful of matters he does not understand - the plain rule is to be a party to nothing underhanded or mysterious, and never to put his foot where he cannot see the ground. 