The writer expresses profound gratitude and delight upon receiving a letter from Diderot, likening it to the joy a wounded soldier would feel if a celebrated general had written to him. Despite their own declining health and the encroachment of death, they remain in high spirits and reflect on the transient nature of life. They praise the artistic talents of various figures, noting the unique genius of La Fontaine and others, and express deep respect and admiration for the recipient, acknowledging their own limited capacity to engage fully due to illness.