Kant's Analytic-Synthetic Dichotomy

In his Critique of Pure Reason, Immanuel Kant defines a synthetic judgments as one in which the predicate “B lies outside of the concept A, though connected with it,” as opposed to analytic ones in which “the predicate B belongs to the subject A as something which is (covertly) contained in the concept A”. He then proceeds to refer to analytic judgments as “elucidatory” since nothing is added to the concept by means of the predicate, the concept is merely broken into its constituent parts , and to the synthetic judgments as “expansive” since they add to the concept a predicate that was not hitherto thought in it. Kant's example for an analytic judgment was “All bodies are extended” since our very concept of any body includes a concept of extension, all we need to analyze it, to “become conscious of the manifold that I always think in it.” Nevertheless, since the two concepts are tautological, though, the judgment “All bodies are extended” not enlarge our knowledge of what a “body” is. Similarly, he gives as an example for a synthetic judgment: “All bodies are heavy” where we are adding to the concept of a body, a predicate that is quite different from the concept, and it is by this process magnifying our knowledge of the body. From the above it then follows that all analytic judgments must be a priori since it is by analysis we are discovering the predicates that, by their very nature, accompany our concepts (experience cannot change that fact that in our concept of a body is included the predicate of being extended), and that all empirical judgments are synthetic (synthetic a posteriori) since here we are adding, by the process of experience, predicates onto our concepts (it is by experience that we base the synthesis of the concept of a body, and the predicate of weight).

This leads to the problem of the possibility of synthetic a priori judgments since if I am to reach beyond the concept A, and synthesize it with another concept B, then what is the justification behind that act of synthesis, for there is not experience to guide me. Investigating this, Kant, whom I shall quote at length here, ponders about causation saying:

Take the proposition: Everything that happens has its cause. In the concept of something that happens I do indeed think an existence preceded by a time, ect., and from that analytic judgments can be obtained. But the concept of a cause is entirely outside that concept and indicates something different from that which happens; hence it is no way contained in that representation. How then can I predicate of that which happens something totally different from it, and know the concept of cause, though not contained in the concept of that which happens, as belonging to it, and belonging to it necessarily.

For Kant, the solution to this was that synthetic a priori judgments are the manner by which the human understanding necessarily orders, and unifies its experiences; hence, the synthetic a priori truths, including the truths of mathematics (for the sum of interior angles is not included in the concept of a triangle), are the internal limits of our understanding, they are the manner by which man is condemned to experience his world.

In the end, the difference between synthetic, and analytic judgments is that in the former the predicate is not included in the object, and that in the latter the predicate is included in the concept. In the realm of analytic judgments, the only possibility is the analytic a priori in which one analyzes a concept into its constituent predicates, and Kant's example for such a judgment is “All bodies are extended.” In that of synthetic judgments, there are both synthetic a priori, and synthetic a posteriori judgments with the former being the necessary conditions of experience, and the latter being the result of adding predicates to concepts via experience; Kant gives mathematics as an example of synthetic a priori judgments, and “All bodies are heavy” as an example of a synthetic a posteriori judgment.