Berlin - German Vice-Chancellor Frank-Walter Steinmeier congratulated celebrated philosopher Juergen Habermas on his 80th birthday on Thursday, lauding him as the "European voice of reason."

In a letter to the philosopher Steinmeier wrote, "for decades you have determined the debates of our country and of Europe," and thanked him for his critical enlightenment, "in the best traditions of our country."

"Without you, the thought and political action for a social and democratic Europe would not be possible," said Steinmeier, who is also Germany's foreign minister.

Habermas is a strong proponent of the European Union (EU), which he said could become the first example of a continental alliance of national states.

"Your suggestions and advice have enduringly influenced my political thoughts and actions," Steinmeier said, thanking Habermas specifically for a conversation on Germany's European Union (EU) presidency in 2007.

The German vice-chancellor further thanked the philosopher and political sociologist for his "position and arguments on the question of the Iraq war."

Habermas was critical of former US President George W Bush's policy on Iraq, saying he had made the world "less safe," whilst ignoring the fundamental values of America's own political tradition.

The works of Habermas examine the concept of the public sphere, asking which is the best form of "discourse" to organise a democratic society.

Habermas' publications include The Structural Transformation of the Public Sphere (1962) and Theory of Communicative Action (1981), both considered seminal works of modern-day philosophy. (dpa)