Te spodnje odstavke si velja nekajkrat prebrati, ko se zalotimo, da o prihodnosti razmišljamo tehnično in premočrtno – na podlagi preteklih trendov in pričakovane statistične verjetnosti posameznih dogodkov.

Seveda je bil John M. Keynes tisti, ki je dvakrat opozoril (leta 1921 v “A Treatise on Probability” in leta 1936 v “The General Theory of Employment, Interest and Money“) na to, da na prihodnji razvoj dogodkov vplivajo povsem “mehki dejavniki”, kot so pesimizem ali optimizem posameznikov, ki se oblikujejo v širšem okolju nervoze ali histerije ter v osebnem svetu lastne negotovosti in lastne percepcije zunanjih okoliščin, vključno z občutljivostjo na vreme. Sklepanje o prihodnosti na podlagi verjetnosti je še vedno samo verjetnost in ne daje nobene gotovosti glede bodočega razvoja dogodkov. Odločitev je kljub vsem poskusom racionalnih kalkulacij še vedno odvisna le od trenutnega sentimenta oziroma “navdiha” posameznikov, izid akcije pa predvsem od sreče in slučajnih dogodkov.

This means, unfortunately, not only that slumps and depressions are exaggerated in degree, but that economic prosperity is excessively dependent on a political and social atmosphere which is congenial to the average business man. If the fear of a Labour Government or a New Deal depresses enterprise, this need not be the result either of a reasonable calculation or of a plot with political intent;—it is the mere consequence of upsetting the delicate balance of spontaneous optimism. In estimating the prospects of investment, we must have regard, therefore, to the nerves and hysteria and even the digestions and reactions to the weather of those upon whose spontaneous activity it largely depends.

We should not conclude from this that everything depends on waves of irrational psychology. On the contrary, the state of long-term expectation is often steady, and, even when it is not, the other factors exert their compensating effects. We are merely reminding ourselves that human decisions affecting the future, whether personal or political or economic, cannot depend on strict mathematical expectation, since the basis for making such calculations does not exist; and that it is our innate urge to activity which makes the wheels go round, our rational selves choosing between the alternatives as best we are able, calculating where we can, but often falling back for our motive on whim or sentiment or chance.

John M. Keynes, The General Theory of Employment, Interest and Money, Chapter 7, 1936

…

[…] I have argued that only in a strictly limited class of cases are degrees of probability numerically measurable. It follows from this that the ‘mathematical expectations’ of goods or advantages are not always numerically measurable; and hence, that even if a meaning can be given to the sum of a series of non-numerical ‘mathematical expectations’ not every pair of such sums are numerically comparable in respect of more and less. Thus even if we know the degree of advantage which might be obtained from each of a series of alternative courses of actions and know also the probability in each case of obtaining the advantage in question, it is not always possible by a mere process of arithmetic to determine which of the alternatives ought to be chosen. If, therefore, the question of right action is under all circumstances a determinate problem, it must be in virtue of an intuitive judgment directed to the situation as a whole, and not in virtue of an arithmetical deduction derived from a series of separate judgments directed to the individual alternatives each treated in isolation.

It has been pointed out already that no knowledge of probabilities, less in degree than certainty, helps us to know what conclusions are true, and that there is no direct relation between the truth of a proposition and its probability. Probability begins and ends with probability. That a scientific investigation pursued on account of its probability will generally lead to truth, rather than falsehood, is at the best only probable. The proposition that a course of action guided by the most probable considerations will generally lead to success, is not certainly true and has nothing to recommend it but its probability.

John M. Keynes, A Treatise on Probability, Chapter 26, 1921