The Professor uses an allusion to express disdain for Ossipon's idea of England as the only safe haven for anarchists. His words introduce the reader to his critical perspective on the country’s state of decay:
‘The social spirit of this people is wrapped up in scrupulous prejudices, and that is fatal to our work. You talk of England being our only refuge! So much the worse. Capua! What do we want with refuges? Here you talk, print, plot, and do nothing. I daresay it’s very convenient [...]'
The allusion to "Capua" is shorthand for the phrase “Capua corrupted Hannibal." This historical allusion refers to the dangers of complacency. Capua was an Italian city which Hannibal, a Carthaginian general, conquered in his battles against the Roman empire in about 212 B.C.E. It is commonly believed that the luxury and comfort of Capua—an affluent city full of good food and wine—led to the previously great general Hannibal's downfall. His soldiers, living in the lap of luxury, became soft and could no longer fight as fiercely as they did before.
By invoking this reference, the Professor suggests that England, with its luxuries and comforts, has lost its vigor and is on a downward trajectory, much like Hannibal and his army after their time in Capua. Like Hannibal’s army, the Professor thinks the English have gone soft, and that their “social spirit” is wrapped up in laws that don’t serve them. Rather than being fiercely dedicated to freedom, the English have become too comfortable with their wealth and their influence. As such, they’re in danger of losing it.