I mean the predilection for certainty...

I mean the predilection for certainty, which is a constant of the modern spirit, just like the energetic and cyclic irrationalist reactions. Obsession with certainty and sceptical desperation are mutual causes of each other like pre-Socratic opposites. We shall speak of this in section 2 (‘Modern Age and Actual Age: from the search for certainty to fallibilism’) . Secondly, we must go through the Aristotelian concepts which may, in my opinion, take us out of this thankless to-ing and fro-ing.

What I mean basically is the Aristotelian notions of prudence ( phronesis ) and practical truth ( aletheia praktike ). In section 3 (Prudence in Aristotle) , I shall set out the contents of Aristotelian prudence and the contribution that it can make to the present debate. An analogous study of the notion of practical truth will be set out in the second part of this paper[^3] .

The concept of prudence is one that has been taken from the area of Aristotelian practical philosophy, where absolute certainty is not expected, but neither are decisions left to mere arbitrariness or imposition. The novelty consists in that, when we recognize, as we do today, that science itself is a human action, the notion taken from practical philosophy may be used for understanding and integrating scientific rationality.

When science is characterized as an activity governed by prudence, it moves away from both the logicist and the irrationalist poles, from the obsession with certainty and from the ‘anything goes’, from algorithm and anarchism. Furthermore, if science is made a prudential activity, it will be much easier for us to connect its particular way of rationality with that of discussions, decisions and environmental actions.

Although it is true that Aristotelian notions can be suggestive, it is not true that they do no more than answer contemporary questions. For them to be active in the on-going debate on the relationship between theoretical reason and practical reason, they must be developed, updated through contemporary texts.

The profit from this manœuvre is double: it makes Aristotle’s concepts available for the present debate and gives some contemporary ideas a very comprehensive and fertile philosophical framework, the Aristotelian framework. In the remaining sections. I shall try to bring to the current debate the Aristotelian notion of prudence through the fallibilism of Peirce and Popper and through Hans Jonas’ imperative of responsibility.