of objects, the unifying combination or elaboration of a given manifold, the forming of a material content.  Rationalists and empiricists alike have been deceived in regard to the necessity for co-operation between the senses and the understanding.  Sensibility furnishes the material manifold, which of itself it is not able to form, while the understanding gives the unifying form, to which of itself it cannot furnish a content.  “Intuitions without concepts are blind” (formless, unintelligible), “concepts without intuitions are empty” (without content).  In the one case, form and order are wanting; in the other, the material to be formed.  The two faculties are thrown back on each other, and knowledge can arise only from their union.

A certain degree of form is attained in sense, it is true, since the chaos of sensations is ordered under the “forms of intuition,” space and time, which are an original possession of the intuiting subject, but this is not sufficient, without the aid of the understanding, for the genesis of knowledge.  In view of the a priori nature of space and time, though without detraction from their intuitive character (they are immediate particular representations), we may assign pure sensibility to the higher faculty of cognition and speak of an intuiting reason.

The forms of intuition and of thought come from within, they lie ready in the mind a priori, though not as completed representations.  They are functions, necessary actions of the soul, for the execution of which a stimulus from without, through sensations, is necessary, but which, when once this is given, the soul brings forth spontaneously.  The external impulse merely gives the soul the occasion for such productive acts, while their grounds and laws are found in its own nature.  In this sense Kant terms them “originally acquired,” and in the Introduction to the Critique of Pure Reason declares that although it is indubitable that “all our knowledge begins with experience (impressions of sense), yet it does not all arise from experience.”  That a representation or cognition is a priori[1] does not mean that it precedes experience in time, but that (apart from the merely exciting, non-productive stimulation through impressions already mentioned) it is independent of all experience, that it is not derived or borrowed from experience.

[Footnote 1:  The terms a priori representation and pure representation (concept, intuition) are equivalent; but in judgments, on the other hand, there is a distinction.  A judgment is a priori when the connection takes place independently of experience, no matter whether the concepts connected are a priori or not.  If the former is the case the a priori judgment is pure (mixed with nothing empirical); if the latter, it is mixed.]