Why are marginalist ideas and economists mainly antagonistic towards their classical predecessors?

. . . as answered on Quora. . . .

Is this true? Are they? Were they? Of the marginalists I have read, they acknowledge the great successes of their predecessors.

Indeed, after writing the Grundsätse — which provided a more coherent foundation for value and price — Carl Menger went on to tutor Crown Prince Rudolf of Austria, and spent most of his economic teaching effort emphasizing, not disputing, classical doctrines.

W.F. Lloyd, a brilliant precursor, built off of Say’s Law of Markets, sparing us the invective.

W.S. Jevons, the most anti-Ricardian of the bunch — and it was against David Ricardo whom he directed most of his ire, if memory serves — was filled with admiration for predecessors in the French Liberal School, and his never-finished Principles of Economics contains this reverential preamble:

An excellent way to begin a treatise on economics is to notice and analyse the manner in which [Nassau] Senior treats the subject in his work on Political Economy. It would be difficult, indeed, to find anything more logical and accurate than the few first pages of this excellent introduction to the science. As we shall afterwards see, Senior may not have followed his own ideas to their ultimate result; but, so far as they go, they form the best exposition of the basis of economics.

Now, I read Senior before Jevons, and I heartily concur. What a mind Senior had! He is my favorite classical-era economist. But he was also part of the Oxford catallactic trend, which was mostly uncomfortable with Ricardian economics and labor theories of value and cost. It was filled with proto-marginalists, like Lloyd. And, as H. Dunning Macleod later indicated, it might best be regarded as part of what he called “the Third School of Political Economy,” which dominated French and even American discussion. That is, it was a separate thing.

The marginalists of the last third of the 19th century were plying a new, more precise and even revolutionary theoretical toolkit. But it fit within much of classical theory, and the marginalists on the whole were not too proud. If Jevons seems cantankerous on occasion, remember, it took a long time to get the new ideas accepted, and not a few of those that did accept the ideas, like Alfred Marshall, did so by trying to incorporate the new with the old as half-measures. Austrians and Walrasians, for example, came to hone their ideas over time, making them more sui generis, inevitably finding the Marshallian/Clarkian mainstream antagonistic to them. So some of the later antagonisms to the classicals we cannot help but note — especially among some of Ludwig von Mises’ students, like Murray N. Rothbard — are no doubt the result of long-festering disputes in which the dominant school was more dismissive than anything else . . . in the manner dominant schools tend to be. And those dominant schools (which went through a Walrasian phase, to make this more complicated) tend to carry on old mistakes while scoffing at the objections of the economists they, in effect, “marginalize.”