The American historian H. Arnold Barton has characterised Birckner, along with Niels Ditlev Riegels, as being "one of the most original thinkers" of the radical group of authors in Denmark in this period.
At age three, he lost his mother Anna Marie (born Wiborg), and half a year later his father, brickmason Johan Michael Birckner, died.
He had also spent his time at the university studying philosophy and philology, and he especially excelled in modern languages, he spoke German like a native and he wrote verses in English.
He especially worked on the problem about the freedom of press and its limits, which among other things the recent conviction of the satiric poet Peter Andreas Heiberg had incurred in Danish debate.
He regularly was present by the dinner table of the vicar Frederik Plum, who later became bishop of Fyn, and Birckner found company with which to share his spiritual and philosophical sentiments.
When the bishop of Zealand Nicolai Balle Edinger had reported the poet Malthe Conrad Bruuns recently published book The Catechism of the Aristocrats (Aristocraternes Catechismus, 1796) to the authorities for infringing the press laws, Birckner anonymously published a small tract which criticised the bishop for playing the part of head of police instead of minding his ecclesiastical pursuits.
It was to achieve this goal that he published his major work On the Freedom of the Press and its Law ("Om Trykkefriheden og dens Love", 1797).
In this book he claims the importance of freedom of press as a powerful means of putting ideas into circulation and thereby enlighten the monarch of things that he would otherwise have been ignorant of.
These words were aimed at the reigning crown prince Frederick, who had shown considerable influences from the tolerant enlightenment ideas in his early years on the throne.
However Birckner does propose some limits on the freedom of press, he does not think it should be allowed to publicly call for rebellion, that is urging the people to overthrow the constitution of the state or in other ways oppose the actions of the government with physical force.
This prompted Birckner to publish his Further Reflections on the Freedom of Press and its Laws ("Videre Undersøgelser om Trykkefriheden og dens Love") the following year (1798).
Only at one point in this book does he change his stance from his previous work, and that is only "half unwillingly" he thinks that writers who "with their filthy imagination attempts to awaken impure desires in his readers", these individuals should be sentenced "a fitting punishment".