Political space rests on the distinction between facts and opinions.

All participants recognise certain facts. Opinions are always based on facts. These facts, even though they may be interpreted differently, have to be acknowledged by everyone. Facts are very popular among debaters precisely because they are unalterable, because there can be no two opinions about them. Those who ignore or deny obvious facts will not be taken seriously by their peers; they will instead be considered to be out of tune with reality.

“Conceptually, we may call truth what we cannot change; metaphorically, it is the ground on which we stand and the sky that stretches above us.” (BPF: 313)

Facts and opinions are clearly not the same. According to Arendt, articulating and exchanging opinions is an important form of political action. Searching for, proving, publishing or stating facts, however, is not. This means that everybody – especially scientists and experts -, as far as they are concerned with matters of fact, are not political actors; and that all questions – Is it correct…?, Is it possible…?, Did they really…?, Will there maybe..?, How can we…? -, as far as they can be answered by simple facts or probabilities (which may of course be the result of the most complicated calculations), are not political questions.

Arendt has often been criticised for her sharp distinction of the political realm. It has been argued, for example, that her understanding of “the political” makes it impossible to discuss important social questions, for example poverty, in political terms. This is not true. Arendt does not argue that these issues are per se not political. Rather, she emphasises that they are political only in certain ways and, most importantly, that they have to be made political. As long as the poor, to stick with our example, just want a bigger piece of the cake or sometimes just a few crumbles to fill their bellies, their demands are not political but purely economic and, in the worst case simply a matter of life and death. In this situation we are not confronted with opinions, but with “hard facts”. Similarly, the solution of the problem does not require the exchange of opinions but either more or a different distribution of the existing resources. There can be different possibilities, but it is a matter of calculation and expertise to find the best one, that is, the most efficient solution. We are confronted with a question of necessity and its technical or administrative solution. Poverty only becomes a genuinely political issue insofar as we discuss it in such a way that our discussion really allows for different opinions, insofar as it becomes a matter of principle, insofar as we have a choice, insofar as it is a question of how we want to live together.

In reality, we are of course not confronted with a black and white scheme of political and nonpolitical questions. One look at the discussion of a Basic Unconditional Income is enough to see that there are political and non-political sides to one and the same question. The important thing is to keep these two sides apart.

Despite the important differences between opinion and truth, whether factual or philosophical, they are not opposites. They “belong to the same realm. Facts inform opinions, and opinions, inspired by different interests and passions, can differ widely and still be legitimate as long as they respect factual truth.” (BPF: 234) The opposite of factual truth is not opinion but the deliberate lie. While opinions are simply different from facts, lies turn facts upside down.

Facts, in other words, limit the range of opinion, interpretation and debate. “And it is only by respecting its own borders that this realm, where we are free to act and to change, can remain intact, preserving its integrity and keeping its promises.” (BPF: 259) We must therefore be very careful not to speak of opinions as if they were facts or about facts as if they were opinions. Further, we must try our best to prevent participants from lying since lies, too, threaten the integrity of the political realm, for example by making false promises; or destroy it altogether, for instance through false accusations.

Political action, insofar as it is an exchange of opinions, is limited by factual truth. Crossing these limits threatens the integrity of the political realm. Therefore, political space depends on the clear distinction of opinions and facts.