In Oliver Twist, Dickens did not try to sugar coat the criminal world. He described this world frankly.
This was clear in his "to show [criminals] as they really are forever skulking uneasily through the dirtiest paths of life...would be a service to society."
Dickens believed that by showing the real picture of the criminal world as it is (realism), the society would be inspired and motivated to find effective solutions to solve this problem.