An introduction to the vague demand theory ; Une introduction à la théorie de la demande floue
(.) At the time when the flare subset theory gave its first applications in economic science, this result is quite intuitive. However, in the following lines, I propose that the cause should be examined in terms of the lack of precision which characterises consumer preferences, the rationality of which therefore becomes less inhuman than that of homo-economicus. Indeed, we know that the axioma of the existence of a preferential order presupposes a consumer with supra-rationality. For example, since an indifference curve is the expression of an infinite set of sets considered to be equivalent, the homo-economicus is supposed to be able to compare one thousand units of a good X and ten units of a good Y with an infinite number of other sets of those two goods. That reason exists only for economic theory. In fact, comparisons and choices are made on quantities which do not have the precision of the numbers they represent. After recalling the traditional framework of demand theory (0), we will assume that a consumer is capable of making comparisons between blurred sets, that is to say, to consider as equivalent 'approximately x units of good X with just less y units of good Y' and 'approximately x' units of X with just over y units of Y'. A vague demand, the graphic representation of which reflects Jean MARCHAL's 'spindle', will ultimately be derived by introducing budgetary constraints (in the sense of the traditional theory of consumer choices). This "weakened" rationality does not lead to an appetite for demand theory. On the contrary, it leads to a more general case where the traditional demand curve appears to be a particular case of the graphical expression of blurred demand. The analysis of consumption choices presented in this introduction is based on a very simple example which does not reveal all the concepts formed by economic theory. This simplification was necessary in so far as it was a question of establishing the general framework of the vague demand theory. ; (.) A l'heure où la théorie des ...
