The word "chains" is used in the Letter to Directory to invoke the image of slavery and oppression. The speaker is arguing that the French Revolution has broken the chains of the past and that the people of France are now free. He uses the word "chains" to symbolize the restrictions that were placed on the people of France before the Revolution, and he argues that these restrictions have now been removed. The image of chains is also used to symbolize the power of the people, and the speaker argues that the people of France are now the ones who hold the power.