No, plenty of -- most? -- concepts are also a posteriori, in Kant's scheme of things.
So, would it be right to say that while many - most - concepts are a posteriori, their analysis is a priori? In other words (?), whatever the concept's origin, once we analyze the concept, our analysis is a priori. That doesn't make immediate sense, but it could be that he's saying that it is how we analyze that is a priori, even if what we analyze isn't ("analyze" here specifically meaning only our extrapolating from what's already in ("in") the concept). And "analysis" means applying the law of contradiction.
The relevant Kant sentence is:
All analytical judgments depend wholly on the law of Contradiction, and are in their nature a priori cognitions, whether the concepts that supply them with matter be empirical or not.
My question for Kant would have been, "What is the difference between analyzing a concept and making it up?" E.g., Kant can (and did) say that "Bodies have extension" is analytic whereas "Bodies have weight" is not, since extension is already contained within the concept "body," whereas weight is not. But can't someone else say, "Well, weight is within my conception of body"? And can't a third say "According to my concept of body, bodies only need to appear to have extension, even if they don't"?
Re: Things that are slightly wrong here, Kant-wise (i)
So, would it be right to say that while many - most - concepts are a posteriori, their analysis is a priori? In other words (?), whatever the concept's origin, once we analyze the concept, our analysis is a priori. That doesn't make immediate sense, but it could be that he's saying that it is how we analyze that is a priori, even if what we analyze isn't ("analyze" here specifically meaning only our extrapolating from what's already in ("in") the concept). And "analysis" means applying the law of contradiction.
The relevant Kant sentence is:
All analytical judgments depend wholly on the law of Contradiction, and are in their nature a priori cognitions, whether the concepts that supply them with matter be empirical or not.
My question for Kant would have been, "What is the difference between analyzing a concept and making it up?" E.g., Kant can (and did) say that "Bodies have extension" is analytic whereas "Bodies have weight" is not, since extension is already contained within the concept "body," whereas weight is not. But can't someone else say, "Well, weight is within my conception of body"? And can't a third say "According to my concept of body, bodies only need to appear to have extension, even if they don't"?