[1][2] After completing his secondary education he attended Lwow University, where he met his future wife, Wanda Zieleniewska.

[3] After Poland regained independence, he became the first Polish Minister of Foreign Affairs, serving in the government of Jędrzej Moraczewski from 17 November 1918 to 16 January 1919.

He researched linguistics (particularly Slavic languages), ethnography of the Central and Eastern European lands, and history of literature.

Supporter of Międzymorze federation idea, as well as Prometheism, he was also a vocal opponent of polonization, arguing that Ukrainians and Belarusians living in Poland should be allowed to assimilate into Polish society at their will and speed.

Author of many works, among them Litwa i Białoruś ("Lithuania and Belarus", 1912), Ukraińska sprawa narodowa w jej rozwoju historycznym ("The Ukrainian National Cause in its Historical Development", 1925), Zarys dziejów PPS ("A Short History of the PPS", 1925), Józef Piłsudski, jakim go znałem ("Józef Piłsudski, as I knew him", 1935).