Theory of Probability

2Concerning Certainty and Uncertainty

2.1 Certainty and Uncertainty

2.1.1. In almost all circumstances, and at all times, we all find ourselves in a state of uncertainty.

Uncertainty in every sense.

Uncertainty about actual situations, past and present (this might stem from either a lack of knowledge and information, or from the incompleteness or unreliability of the information at our disposal; it might also stem from a failure of memory, either ours or someone else’s, to provide a convincing recollection of these situations).

Uncertainty in foresight: this would not be eliminated or diminished even if we accepted, in its most absolute form, the principle of determinism; in any case, this is no longer in fashion. In fact, the above‐mentioned insufficient knowledge of the initial situation and of the presumed laws would remain. Even if we assume that such insufficiency is eliminated, the practical impossibility of calculating without the aid of Laplace’s demon would remain.

Uncertainty in the face of decisions: more than ever in this case, compounded by the fact that decisions have to be based on knowledge of the actual situation, which is itself uncertain, to be guided by the prevision of uncontrollable events, and to aim for certain desirable effects of the decisions themselves, these also being uncertain.

Even in the field of tautology (i.e. of what is true or false by mere definition, independently of any contingent circumstances), we always find ourselves in a state of ...