In 1830, the first philosophical writings of Alexandru Hajduu - About the Divine Poetry Quality and About the Purpose of Philosophy - are published in the Moscow magazine "Vestnik Evropa".

On June 24, 1840, he held a famous speech in front of the graduates and pedagogical staff of the county school in Hotin - The souvenirs from the past, which is the present and shows the future of Moldova, translated immediately in Romanian by Constantin Stamati.

In this period he wrote the study "The Problem of Our Time" which will be translated and published in Bucharest only in 1938.

Hâjdeu made an important contribution to the unification of the Romanian Principalities, especially, through his speeches held in 1837 and 1840.

His speech held in 1837 and then, published in 1838 in Brașov and in 1839 in Bucharest, was the cornerstone of the unification of the Romanian Principalities on January 24, 1859.