Tom’s Gang, like society, is rooted in arbitrary traditions that have lost their meaning. The boys don’t know what ransoming is, but adopt it as a practice only because of tradition. While it is okay for a make-believe gang to do so, it is childish for adults in society to do so, especially considering that, while the violence done by Tom’s gang is pretend, that perpetrated by society is very real, with bloody, sometimes deadly consequences. This passage also points out how ridiculous it is to obey the letter of Christianity but not the spirit: the boys are going to do something bad, rob people, but insist that they can’t do it on Sunday, because Sunday is a holy day. But wicked things are no more wicked on one day than another—the boys are mixing up
looking like good Christians with actually
being good Christians, just as it becomes clear many adults also do.