It is quite incorrect to say, as has been sometimes said, that the mediæval just price was in no way different from the competition price of to-day which is arrived at by the higgling of the market. Dr. Cunningham is very explicit and clear on this point. 'Common estimation is thus the exponent of the natural or normal or just price according to either the mediæval or modern view; but, whereas we rely on the higgling of the market as the means of bringing out what is the common estimate of any object, mediæval economists believed that it was possible to bring common estimation into operation beforehand, and by the consultation of experts to calculate out what was the just price. If common estimation was thus organised, either by the town authorities or guilds or parliament, it was possible to determine beforehand what the price should be and to lay down a rule to this effect; in modern times we can only look back on the competition prices and say by reflection what the common estimation has been.'[1] 'The common estimation of which the Canonists spoke,' says Dr. Ryan, 'was conscious social judgment that fixed price beforehand, and was expressed chiefly in custom, while the social estimate of to-day is in reality an unconscious resultant of the higgling of the market, and finds its expression only in market price.'[2] The phrase 'res tanti valet quanti vendi potest,' which is so often used to prove that the mediæval doctors permitted full competitive prices in the modern sense, must be understood to mean that a thing could be sold at any figure which was within the limits of the minimum and maximum just price.[3] [Footnote 1: _Growth of English Industry and Commerce_, vol. i. p. 353.] [Footnote 2: _Living Wage_, p. 28.] [Footnote 3: Lessius, _De Justitia et Jure_, xxi. 19.] The last sentence suggests that the just price was not a fixed and unalterable standard, but was somewhat wide and elastic. On this all writers are agreed. 'The just price of things,' says Aquinas, 'is not fixed with mathematical precision, but depends on a kind of estimate, so that a slight addition or subtraction would not seem to destroy the equality of justice,'[1] Caepolla repeats this dictum, with the reservation that, when the just price is fixed by law, it must be rigorously observed.[2] 'Note,' says Gerson, 'that the equality of commutative justice is not exact or unchangeable, but has a good deal of latitude, within the bounds of which a greater or less price may be given without justice being infringed;'[3] and Biel insists on the same latitude, from which he draws the conclusion that the just price is constantly varying from day to day and from place to place.[4] Generally it was said that there was a maximum, medium, and minimum just price; and that any price between the maximum and minimum was valid, although the medium was to be aimed at as far as possible. [Footnote 1: II. ii. 77, 1, ad. 1.] [Footnote 2: _De Cont. Sim._, 58.]