I don't want to ruin the plot for other viewers, so I will generalize concepts. However, I will assume you've already watched previous episodes.The theme of this episode could be the circle of life. Boone's incident coincides with Claire's. One person leaves, another arrives. This also brings balance to the show. It seems the island is pushing and pulling at the group in order to establish equilibrium. The sorrow versus joy . The break in the marriage of Jin and Sun versus their unity in courageously helping the two people most in need. Locke's use of his legs gets taken when he tries too hard to open the hatch. He abuses Boone's help and refuses to submit to the impenetrable hatch, and uses his legs selfishly instead of hunting for food for the group. So his legs are taken from his control, except for the purpose of helping Boone. The island is teaching him to give selflessly, and it is pulling things into balance whenever they teeter either way. This balancing seems to be the broader theme of Lost. Note also in a previous episode the boat being built and then burnt.