Son of the famous chemist Marcellin Berthelot, the young Philippe was reared in the society of illustrious literary and scientific figures. He began his diplomatic career in 1889, serving in China from 1902 to 1904, when he entered the Ministry of Foreign Affairs. At the outbreak of World War I, he was active in Balkan negotiations and served in inter-Allied liaison. After participating in the Versailles Peace Conference, he was appointed in 1919 as the director of political and commercial affairs and counsellor of state, one of the highest positions in the ministry. In September 1920 the post of secretary general was created expressly for him. In 1921 he resigned after being accused of using his influence improperly in connection with the affairs of the Industrial Bank of China, of which his brother was a director. Reappointed secretary general in 1925, he accompanied Briand to Locarno and to London and conducted negotiations for resuming Franco-Russian relations. From then until 1932 he virtually controlled the internal organization of the ministry, following a policy that he described as one of “close union with England and of rapprochement with Germany.” Ill health forced his resignation in 1932, and he died of a heart attack two years later.