the proof of the pudding is in the eating

"The proof of the pudding is in the eating" is an idiomatic expression that means the true value, quality, or effectiveness of something can only be determined by experiencing or testing it firsthand. It suggests that theories, promises, or claims are meaningless until put into practice and proven to work. Just as the real quality of a pudding is judged by how it tastes when eaten, the phrase emphasizes the importance of practical results rather than mere speculation or promises.