Critique of Judgement: Part I, Analytic of the Beautiful, Fourth Moment, §§ 19 and 20: The Subjective Necessity, Which We Ascribe to the Judgement of Taste, Is Conditioned; The Condition of Necessity Which a Judgement of Taste Asserts Is the Idea of a Common Sense
The judgement of taste requires the agreement of every one; and he who describes anything as beautiful claims that every one ought to give his approval to the object in question and also describe it as beautiful. The ought in the aesthetical judgement is therefore pronounced in accordance with all the data which are required for judging and yet is only conditioned. We ask for the agreement of every one else, because we have for it a ground that is common to all; and we could count on this agreement, provided we were always sure that the case was correctly subsumed under that ground as rule of assent.
§ 20. The Condition of Necessity Which a Judgement of Taste Asserts Is the Idea of a Common Sense
If judgements of taste (like cognitive judgements) had a definite objective principle, then the person who lays them down in accordance with this latter would claim an unconditioned necessity for his judgement. If they were devoid of all principle, like those of the mere taste of sense, we would not allow them in thought any necessity whatever. Hence they must have a subjective principle which determines what pleases or displeases only by feeling and not by concepts, but yet with universal validity. But such a principle could only be regarded as a common sense, which is essentially different from common Understanding which people sometimes call common Sense (sensus communis); for the latter does not judge by feeling but always by concepts, although ordinarily only as by obscurely represented principles.
Hence it is only under the presupposition that there is a common sense (by which we do not understand an external sense, but the effect resulting from the free play of our cognitive powers)—it is only under this presupposition, I say, that the judgement of taste can be laid down.