The doorknocker is an important object, though. The doorknocker showed Scrooge Jacob Marley's face, in which led him through the events of the "night before Christmas" Without have seeing Jacob Marley's face he wouldn't have had any motivation.
The two themes are 1) The goals of an individual are meaningful and 2) One should be open to new experiences.
Everybody has his or her own personal goal. Every goal of an individual is meaningful regardless if the other finds said goal unimportant. Pursuing personal goals is very meaningful to the individual because it gives him or her the purpose and motivation to succeed in his or her desired goal.
One should be open to new experiences. This is part of our growth as a human person. If we are afraid to try new experiences and prefer to live within our comfort zones, we will become stagnant and our growth and development as an individual will be hindered. We will also become blind to new discoveries which may enrich our lives.
