After thus criticising the formula--Homo Mensura--Plato proceeds to canvass the other doctrine, which he ascribes to Protagoras along with others, and which he puts into the mouth of Theætêtus--"That knowledge is sensible perception". He connects that doctrine with the above-mentioned formula, by illustrations which exhibit great divergence between one percipient Subject and another. He gives us, as examples of sensible perception, the case of the wind, cold to one man, not cold to another: that of the wine, sweet to a man in health, bitter if he be sickly.[81] Perhaps Protagoras may have dwelt upon cases like these, as best calculated to illustrate the relativity of all affirmations: for though the judgments are in reality both equally relative, whether two judges pronounce alike, or whether they pronounce differently, under the same conditions--yet where they judge differently, each stands forth in his own individuality, and the relativity of the judgment is less likely to be disputed. [Footnote 81: Plato, Theætêt. pp. 152 A, 159 C.] [Side-note: Such is not the case with all the facts of sense. The conditions of unanimity are best found among select facts of sense--weighing, measuring, &c.] But though some facts of sense are thus equivocal, generating dissension rather than unanimity among different individuals--such is by no means true of the facts of sense taken generally.[82] On the contrary, it is only these facts--the world of reality, experience, and particulars--which afford a groundwork and assurance of unanimity in human belief, under all varieties of teaching or locality. Counting, measuring, weighing, are facts of sense simple and fundamental, and comparisons of those facts: capable of being so exhibited that no two persons shall either see them differently or mistrust them. Of two persons exposed to the same wind, one may feel cold, and the other not: but both of them will see the barometer or thermometer alike.[83] [Greek: Pa/nta me/trô| kai\ a)rithmô=| kai\ stathmô=|]--would be the perfection of science, if it could be obtained. Plato himself recognises, in more than one place, the irresistible efficacy of weight and measure in producing unanimity; and in forestalling those disputes which are sure to arise where weight and measure cannot be applied.[84] It is therefore among select facts of sense, carefully observed and properly compared, that the groundwork of unanimity is to be sought, so far as any rational and universal groundwork for it is attainable. In other words, it is here that we must seek for the basis of knowledge or cognition.