Concepts as Rules: Kant's Three-Fold Synthesis in the A-Deduction

In Kant's A-Deduction, he introduces the three-fold synthesis to explain how the mind unifies the sensible manifold into a cognition. The first stage of this is the synthesis of apprehension in intuition, where the subject "runs through" and "takes together" the manifold given in sensibility. Kant explains that an intuition provides a manifold, and without this act of apprehension, there is no basis for a unified perception. The second stage of the three fold synthesis is the synthesis of reproduction in the imagination. Because earlier representations disappear the moment new representations arise, Kant explains that the imagination must reproduce them according to associative rules. This reproductive activity enables successive representations to be combined into a single representation. For instance, an object that persists over time. Finally, the synthesis of recognition in the concept is where the subject becomes conscious of the unity achieved as a result of the preceding syntheses, recognizing the manifold as representations of the same object within a concept. Kant explains that without recognizing that what we think right now is identical to what we previously thought, the manifold could never constitute one cognition. All three syntheses are therefore interdependent and jointly required for experience to transpire.

When Kant says that concepts are "rules for synthesis," he means that concepts provide the structure under which the manifold is taken as belonging to one object. These concepts determine the unity that the manifold must exhibit in order to count as a representation of a single, identifiable thing.

This claim can be interpreted in two different ways. The first interpretation is that concepts guide the imagination by directing how the manifold should be combined. For instance, the concept of a house instructs the imagination on how to organize its perceptual parts into a unified whole. A challenge of this conceptualist view is explaining how empirical concepts could ever be acquired if they were required for perceiving their own instances. The second interpretation distinguishes imaginative synthesis from conceptual judgment. This interpretation explains that the imagination operates blindly according to laws of association, while concepts provide rules for judging which associations are objectively valid. This reading fits Kant's remark that the understanding can make no other use of concepts than to judge by means of them: concepts determine whether an associative combination corresponds to how things objectively are, rather than to a merely subjective train of thought.